New iMac + Lion + Video = Freeze – Updated

See an expanded version of this article on TidBITS.

I’ve generally been fortunate when upgrading to new versions of OS X, but this time I’ve been hit with a nasty bug, that’s already caused me to lose some work. I have a new 27″ iMac, purchased in early June. This computer worked fine under Snow Leopard, but once I installed Lion, I started seeing random freezes when viewing videos. The videos could be any kind – Flash, H-264 or QuickTime – and the freezes are mean: the entire screen locks up, except for the cursor, and, while sound continues if I have iTunes playing in the background, I can’t do anything else but a hard restart. Sometimes it simply freezes, and other times I get displays like this (this is a screen shot I took of a QuickTime Player window; my iMac froze when I tried to close the window):

When this happens, the following messages are written to kernel.log:

7/23/11 12:02:40.000 PM kernel: ** GPU Debug Info Start **
7/23/11 12:02:40.000 PM kernel: 0x00006740
7/23/11 12:02:40.000 PM kernel: 0x0000008f
7/23/11 12:02:40.000 PM kernel: 0x00000001
7/23/11 12:02:40.000 PM kernel: 0x00000018
7/23/11 12:02:40.000 PM kernel: 0x0000a880
[and so on for a few hundred lines]

There’s a pretty long thread on Apple’s forums of people confirming that they, too, have this problem, and there are other threads discussing it as well. I called AppleCare on Saturday, and the technician was not aware of this problem. I told him I knew he wouldn’t have a solution, but wanted to make sure that the information got to Apple’s support technicians so it would go up the chain.

For now, I avoid watching any kind of video on my iMac. My MacBook Air has no problem, so I use that. But this is a disturbing problem, clearly related to Lion, which will hopefully be fixed in the first Lion update, which is likely to be released this week.

Update: I got a call back from an Apple technician this afternoon, asking for more information, logs, system profiles, etc. So I can confirm that Apple is indeed looking into this. It was relatively easy to reproduce the problem while on the phone with the technician, alas.

Update 2: The Apple technician has had me try a number of things to eliminate various possibilities – removing certain caches, etc. So far, none of them has led to a solution. The Apple forum thread is getting longer…

Update 3: The Apple technician asked me to test my Mac without the third-party RAM I had added. It froze pretty quickly. But while I was at it, I tried removing the original RAM, and was unable to make it freeze, no matter what kind of videos I viewed, even with many at a time. This may therefore be the culprit, even though a number of people on the Apple forum tested their RAM and found no problems with it.

Update 4: I just had a freeze, so it’s not the RAM. Too bad; that would have been an easy solution.

Update 5: I’ve been working with an Apple engineer for the past week, and he had me try everything suggested in this very long therad. He also asked me to do a clean install on a different disk, which I did yesterday. I was unable to reproduce the problem, despite running lots of videos, sleeping often, etc. This doesn’t mean it won’t happen, but I was able to easily reproduce it on my main boot partition.

There are certainly many variables – the clean install had no third-party sofware installed. But given the number of people posting here, I doubt that there’s any third-party software responsible. (Also, the Apple engineer has seen my crash logs, and hasn’t suggested that any specific software could be responsible.) So I’m a bit flummoxed by this latest development…

Update 6: I was able to get a freeze on my clean install. So that rules out any issues specific to my installation, third-party software, etc.

The story so far: Let me summarize the problem here, and discuss the many solutions proposed on the very, very long Apple forum thread. Viewing videos of any kind cause freezes. This doesn’t happen every time one views a video, and only happens after an iMac has been put to sleep at least once, or, in some cases, multiple times. These videos can be Flash, H-264, or QuickTime formats, and viewing may occur in Safari, Firefox, QuickTime Player, iTunes or any other program.

Doing the usual troubleshooting steps, such as resetting the PRAM or SMC does nothing. Doing a clean installation of Lion, with no third-party software installed, does not solve the problem. Deleting and/or reinstalling Flash has no effect on it. RAM or other hardware has no effect, though it may turn out that this is a hardware problem with video cards. (This seems unlikely, because many people with this problem, including myself, had their iMacs with Snow Leopard, and did not have freezes.) In short, none of the “solutions” offered on the Apple forums resolve the issue, as you can see in the trials I carried out in my various updates above.

For now, all we can do is wait on Apple. I’m willing to give Apple a bye on this for now, but this is starting to become a long time since the discovery of this issue. I can understand the anger of some users, and I’m a bit surprised that Apple didn’t discover this. However, it’s entirely possible that they didn’t have the new iMacs any earlier than users did for testing. (Which is, of course, reprehensible.) While some posters in the Apple forum thread mention similar problems with MacBook Pros, it is not the same problem; iMacs freeze; MacBook Pros seem to have kernel panics, and it seems to be a much more isolated problem.

In any case, I’ll continue updating this post as I get more information.

Update 7: I got some interesting information from someone who knows a lot about graphics cards and drivers. One of the most interesting things he said was that the number of background processes running may have an effect on this issue. This is interesting, because when I tried reproducing it on a clean installation, with no third-party software installed, it took quite some time to induce a freeze. On my normal installation, it’s much easier to reproduce the problem, and I do have a lot of third-party software installed that runs background processes. Nevertheless, this does not offer a solution to the problem, and Apple has still not come forth with anything. This is starting to become a bit long. Sigh.

Update 8: On August 16, Apple released Mac OS X 10.7.1, a small update which claims to “Address an issue that may cause the system to become unresponsive when playing a video in Safari.” It’s not clear whether this resolves the current issue. In my initial tests, I was unable to get my iMac to freeze, though I was seeing some artifacts when starting to play videos using QuickLook. It will take a while to be certain whether or not this resolves the issue. If anyone reading this has applied the update and is still having the problem, please post a comment.

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60 replies
  1. Valentin says:

    Experienced exactly the same problem (27″ iMac 2011). For now I downgraded to 10.6.8 and am looking forward for a quick fix. They must have left the mid 2011 iMac out when testing, I just can’t believe they didn’t run over this huge bug.

  2. Sven says:


    Well – just to confirm that the problem exists with “German iMacs” (well…) too.

    I’ve got my brand new iMac 21.5 i7 just a couple of days before Lion was out, and perhaps I was too fast to update. But I don’t remember if I had the problem one with 10.6 or not. Anyway: It’s annoying. Coming from a PC that was clearly more stable….

  3. Michael C. says:

    Interesting about the RAM. I have the same freezing problem as you, but my iMac only has the Apple supplied RAM. So, if I remove the Apple supplied RAM, I suspect my iMac won’t freeze…but it won’t run either, since it wouldn’t have any RAM at all. ☺

    • kirk says:

      Right, you’d have to get some other RAM and see if it works. I’m hoping some of the other people posting on the Apple forum thread will try and see if it confirms what I’ve seen.

  4. Karel van der V says:

    Same here…. my 21.5 IMAC (bought June 2011) freezed last week 2 times… since then it did not happen. As seen by other threads on macrumors it has to do with (ie.)playing video’s/ flash issue.. Since Apple is working now on it I presume that 10.7.1 will incorporate this by this bug-fix.

    • Michael C. says:

      Much as I dislike Flash, I wouldn’t blame the freezes on it. That’s because I got the same freeze when viewing a straight .m4v file via QuickLook in the Finder.

      I have noticed that it happens much less often (though still occasionally) if I don’t have iTunes running.

  5. Sycren says:

    I upgraded to Lion and had it crashing all the time so I downgraded to Snow Leopard, but the problem is still there, its crashed 5 times today and I only got this new 27 inch iMac on friday :(

    So it seems to be more of a hardware fault

  6. stikfan says:

    Thanks for the info and updates. I am a little worried from your last updates that may not be a solved problem that will just be in 10.7.1.

    I’m also on a new iMac purchased in June, and just Friday I’ve started to get the problem where wifi takes a couple beats to connect and causes Safari, iPhoto, and other apps to report that there is no internet connectivity for minutes. Do you have this problem too?

    I’m glad that I don’t have a POP account or use a NAS, or I think that I’d be pretty pissed right now.

    • kirk says:

      I’ve had some problems with connections dropping, or not being made on awakening my Mac, especially to my 5 GHz network (I have an AirPort Extreme with two networks set up). That, too, only began with Lion.

  7. Ben Sumner says:

    Twice today for me. Most problems I’ve ever had with a Mac product. I have a hard time believing that Apple won’t eventually discover the culprit!

  8. Danny says:

    Same problem here with a 21.5 new iMac I bought in mid June 11. Problem only appeared after installing Lion. Also, mouse cursor seems to move and screen stays in tact, but keyboard is dead and any/all commands don’t work to wake it up, quit or try and restart. Requires manual reset by holding down the power button, this sucks.

  9. Edwin says:

    I just bought my iMAC 27in several days ago and I’m having the same issues, except the freeze only occurs with certain video types.

  10. Jaime says:

    Just bought the iMac Saturday, upgraded to lion and it constantly freezes for videos, but only thru safari. Using firefox now and no freezes yet!

  11. john says:

    yes i have the same thing…iTunes keeps playing but everything else freezes…only solution to hold the off button. how annoying!

  12. Bill Higgins says:

    Thanks very much for the thoughtful and thorough write-up as well as working to make Apple aware of the issue and helping to provide them with diagnostic information.

    As I noted on the Big Long Support Thread, it’s possible to SSH into the hung iMac if you enable Remote Login pre-hang and know its IP address pre-hang. So far though I haven’t been able to glean any useful information while SSH’d into the hung iMac, but perhaps someone with better Mac command line mojo than myself* will be able to figure something else from poking at the hung system via the SSH command line.

    * I.e. Perhaps someone at Apple who is working to diagnose/fix this.

    • kirk says:

      Yes, but as you say, when you do this, you don’t see any stuck processes.

      Apple is working, as I point out. I’ve been in touch with an Apple engineer, run a number of tests, and sent them logs and system info each time. It’s been a while now, but I know there are people working on it, so I hope they’re getting close to a solution. Others have said that the 10.7.2 beta fixes the problem; while I have developer account, I don’t want to install that beta on my iMac, which is my main Mac. This said, I’m not convinced that it does, indeed, solve the problem. You can run for a day and not get freezes under 10.7, as I saw doing several tests (such as removing RAM).

  13. Bill Higgins says:

    I have a support call scheduled for Thursday but am thinking to cancel it because it seems like you are feeding them all of the diagnostic information they should need to troubleshoot the problem. Do you think it does any good to have the support call if nothing else to “vote” on the importance/severity of the problem?

    Also, have you suggested that they simply get a 2011 iMac 27″ and see if they can reproduce it themselves? As the support thread is aptly titled, “OSX Lion + 2011 iMac 27” + Video = Freeze” This iMac only has one model of video card (AMD Radeon HD 6970M, in 1 and 2 GB variations) so it doesn’t seem like there are that many variables.

    • kirk says:

      I think a support call is useful, if you have the time, because it reinforces the extent of the problem. This said, I know the Apple technicians are following the forum thread, so they know there are a lot of people affected.

      Additional information may confirm something that they’re not 100% certain about, so it could be useful. But, to be honest, this has taken a lot of my time, so it depends on whether you can dedicate time to it. Also, it depends on what they ask you to do. The first person who called me back (after the problem was escalated) didn’t even bother with things like PRAM or SMC resets. He just wanted info about my system. He then asked me to try and reproduce with no peripherals, without third-party RAM, etc. None of these things were very time consuming. He never asked me to reinstall Lion, but asked if I could do a clean install on another disk or partition. (I think they have a checkbox on my record for Not a Noob.)

      • Bill Higgins says:

        Good points; I will go through with the call and will make them aware of your prior troubleshooting/interactions so they can more easily correlate the incidents with the problem.

  14. Carl Moebis says:

    Kirk, Awesome compilation. I’ve been active in the forum regarding this issue, and have been trying to draw attention to it from blogs (TUAW / 9to5mac), got them to publish the issue, still ignored by Apple. Called Apple numerous times, most of the techs have no idea what I’m talking about with the issue, and after some convincing they finally believe me. It’s supposed to have been escalated up to engineering, but they can not give me any status updates. This is reprehensible. I’m so pissed at Apple. It started with FCP Pro X and now Lion, since Steve Jobs went on medical leave their QA has gone downhill.

  15. Danny says:

    New July iMac 27 shipped with lion . Experienced same freeze problem just after ripping DVD in handbrake.

  16. Erick J says:

    Same Problem with iMac and OS X Lion, i think 8 times a week my lion on iMac Freezes! #AppleFail #LionFail. Why didn’t they test there software? Are they only looking to de design?! :(

  17. Steve Lin says:

    I have an identical problem on 7,1 iMacs, and I know 8,1 iMacs as well, starting with driver update on 10.6.3. The difference is, we’re able to revert back to 10.6.2 graphic drivers and make the problem go away. It has to be something they changed in driver code. Looks like I’ll be stuck on 10.6.7, hacked to run 10.6.2 graphic drivers, until this is resolved.

    There’s a long thread on support forum about 2007 iMacs and 10.6.3 video freeze also, although probably not as long as 2011 iMacs

  18. Bert Koot says:

    Same problem here. iMac 27″ mid 2011. After upgrade to Lion several freezes a day while playing videos.

  19. Renus says:

    I’m having the same problem. Just got my 21.5″ iMac last week. It’s frozen twice on me. Once with a flash video, once with quicktime in iTunes. I could return the computer, but I think I will just hold out for an Apple update. Computer is fine otherwise.

  20. Lachsack says:

    Hello! I have the same problem on my new iMac 27″ (Mid 2011).

    In my opinion this seems to be a problem with the quicktime-player, because my mac only freezed, when I watched video-files (especially mov-files) with Quicktime-Player. Until now I haven’t had a crash when using VLC.

    But I haven’t had this issue with Snow Leopard, so switching back is an option to think about…

  21. alsays says:

    Just got a new 27 iMac this past week with Lion preinstalled. New to mac and was pretty pleased until the mac started completely freezing. It’s happened several times this week and I noticed it always happened when I tried watching a video. Last night I googled the problem and discovered this is a widespread problem. I’ll be calling apple in the morning.

  22. F.D.Mulder says:

    Received an iMac 27″ about an hour ago, purchased at the Dutch Apple Store. (Lion installed)
    During initial setup, in the “snapshot” phase, the computer froze, with only the mouse cursor alive.
    Wow! Back to 10.6 for now.

  23. JohSm says:

    My New iMac 21.5″ i5 / 6770 was delivered with 10.7 (Lion) and i constantly have this problem after suspend/sleep.

    Have talked alot with Apple support, and done all the things they wanted including a factory reinstall (formatting the drive first.)
    Installed Lion over internet as there is no DVD’s or restore CD’s delivered with the new iMac’s and it takes a couple of hours to do that..

    It didn’t help!

    However it worked with Quicktime playback (tried it a couple of times after suspen/sleep) after the reinstall, until i started iTunes for the first time! Then the problem came back, now Quick time and iTunes always hangs during video playback efter it’s been in Suspend/sleep mode…

    Maybe i just was lucky the first tries with Quicktime playback or maybe iTunes screws something when you do use it the first time… (Output to AppleTV 2 maybe works.. needs to ty that one.)

  24. JohnA says:

    I’ve been on phone to Apple 4 times today with no success. I have 27″ iMac that was running Leopard fine then I installed Lion. Now when I boot I get spinning pinwheel of death (without even running videos). Can’t do anything. If I safe boot don’t have issue but then don’t have inte

  25. Marcel says:

    Just installed the 10.7.1 update on my 2011 iMac. I have opened several applications and started a video in Quicktime and put it deliberately into sleep.

    Started from sleep and could not reproduce the screen freeze when playing a video. For the time being it seems the problem is solved. I will use the sleep mode again and give it a try to figure out if I just was lucky this time…

  26. Dale says:

    Well.. I’m on day 4 of the 10.7.1 update and my 27″ iMac has gone to sleep many times and I’m happy to report as of today, still no video freezing problems. I hope this trent continues. :-)

    Is everyone else experiening the same good results?

    And Thanks for this blog, this has helped to know I’m not alone with this issue.

  27. Chris says:

    I have been running 10.7.1 and have begun having this problem recently (within the past two weeks). Perhaps I have a different problem, but the symptoms are the same without the green screen. Any word on if there are alternative solutions/causes to this problem? Thanks for the awesome blog posts and chronicling this situation!

    • kirk says:

      Well, 10.7.1 seems to have resolved this particular problem, and yours is likely to be something else. All I can suggest is try some of the things I had to try to fix mine early on, described in the article.

  28. Ben says:

    i had same problem. i did hardware test nothing was found.
    please have this this problem fix soon apple.

  29. Oleksiy says:

    Just happened to my brand new Mac 21.5 8GB mac-RAM while watching a video from youtube in Chrome. Bought it last week of September 2011

  30. Mick W. says:

    I have a mid 2011 27″ iMac running Lion 10.7.2 and I’ve done all the suggested fixes and it’s still freezing. Apple even replaced my HD and that didn’t fix it. Mine freezes in Mail, iTunes, Facetime, Safari, you name it.

    Is there any new info on this problem? Should I demand that they replace my video card?

    • Ben lee says:

      Hi after 10.7.2 update apple didn’t fix the problem at all. But when I run on windows 7 32bit or 64bit didn’t have problem at all. Is anyone same?

  31. Timo says:


    I still have the same problem.
    When ever i watch video, (Netflix, youtube, itunes, etc)
    My computer (IMac) freeses. Only mouse mooves. and nothing else can be done. Only the power button..,

    Hope that someone figures out a solution to this soon.
    It is my first mac with lion (came from shop allready with lion).And the first impression is not so good.

    It does not crash to anything else. only watching videos.

  32. Neilo says:

    This has happened frequently to my 21″ purchased new in August 2011 and over the past 2 weeks I have only intermittently internal or externally boot my computer but now nothing at all.
    The imac came with 10.7 preinstalled and no disks. Updated to 10.7.1 and then .2. Now I’ve taken it back to 10.6 and various points up to 10.6.7 and now my imac is not booting at all anymore.

    I think it’s some sort of hardware issue??

    I’ve been jotting down many more details than below but this basically covers it.

    The last things I’ve done are the following

    Normal boot and use but shortly after using safari rainbow wheeled. Cannot launch any other app but can move around finder/no shutdown prop. No force quit.
    Force powered off.
    Left for a few hours in disgust.
    Boot to question mark.
    Option boot sees no valid sys.
    Reboot to ext 10.6 hd sys to blue screen only (stuck).
    Force powered off & left for 10 min.
    Option boot sees int hd again (why or how I don’t understand).
    Select & booted and stayed on blue screen.
    Force power off.
    A few more time of trying this finally boots my system and I start to simply transfer files only and it stalls again.
    Useless and no idea what could cause this.
    Apple think a simple HD replace but if I can’t boot from an ext HD or DVD then what good would replace of HD do?

  33. Joey says:

    Here are my notes on my particular issue-

    Video “skips”
    Audio (iTunes) skips
    Mouse pointer goes wild, all over screen, skips around, gets stuck in upper left corner
    When typing, characters get “stuck” and repeat, sometimes a few times, sometimes an entire line
    Occasionally randomly asks to restart

    Usually happens when:
    Playing video in Firefox or Safari
    Watching video in iTunes, VLC, or Quicktime
    Running a Flash game for a long time in Facebook, especially if there’s excessive animation

    Occasionally happens when:
    Running mouse pointer along dock
    Growl notifications (shut off now)
    Time Machine updates (when icon spins in menu bar)
    Twitter app updates
    When adjusting volume using keyboard (system volume)

    Attempted fixes:
    Repaired permissions
    Lion recovery
    Installed SL on fresh partition, no additional apps. Opened iTunes with existing playlist (from other partition) and watched movie. Also skipped.
    Removed some apps
    Disabled Time Machine, Growl.

    Sometimes works: Closing some programs.


    I just got off the phone with Apple Support. They could not troubleshoot me because my warranty and Applecare are expired, but I told her I really just wanted to document this problem with Apple Support.

    The first thing I want to say is, if you haven’t contacted Apple already, DO IT. The reason why is because while they do not currently have any known fix or even idea of what the problem is, if more people speak up about the problem they will look at it more closely. If you are on record as having logged your problem, they will contact you regarding it if and when they do find a solution. This is direct from Apple Support, not my opinion.

    She must have done a quick search while on the phone with me, because she did say she sees several discussions of this on the forums, so she was aware that a problem exists.

    She asked me if I had done a clean install and I told her no, that I couldn’t get into Time Machine because it caused a freeze. I did tell her I did a clean install of Snow Leopard on a separate partition, and that the problem appeared on SL as well. I suggested that maybe Lion did a firmware upgrade that also affected the SL partition. She informed me that the last time Apple offered a firmware upgrade it was a graphics upgrade for iMacs to version 3.0, given in August of 2011. As I was still running SL in August, I don’t know that this could really be the cause of the problem.

    She recomended I back up all my important data to another external drive, not Time Machine, and do a totally clean install of Lion and see how that goes.

    She also recommended that, although I no longer had warranty coverage, I could take my iMac to the Genius Bar for a 15 minute diagnostic where they will check the hardware profiles and make sure there are no underlying issues. I believe some people here have already been to the Genius Bar with no success in solving this issue, but I’m just reporting what she told me.

    At this point, I would again reiterate that everyone with this issue absolutely call Apple Support, even if only to log the complaint with a live person. When they actually hear from enough of us they will have to take this more seriously. You can start contacting Apple Support at


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