iMac 24" flickers then freezes (mouse cursor can still be moved)

Discussion in 'iMac' started by macdrive007, May 13, 2011.

  1. macdrive007

    macdrive007 Well-Known Member

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    The 24" iMac 2.93ghz NVIDIA GT120 (early 2009) we use has been working fine until the second half of last year (2010) when the screen suddenly flickers (usually after clicking on safari links quickly one after another, or simply when you click around - does not happen when you leave the iMac alone), then freezes with a 99% chance of non-recovery. However, when you move the mouse, the cursor still moves. Sometimes when we continue clicking at this state, the cursor also stops functioning. Only way to recover is by rebooting, but this problem happens again, usually once every week. We have tried PRAM & SMC reset, also Onyx, Disk Utility and CleanMyMac, it still happens. Disk is verified to be ok. All software updates are installed. Only thing that changed before this happened is we upgraded the RAM to 8gb Gskill brand from the TPC reseller mentioned in one of our Philmug threads, and also upgraded the OS to 10.6.6 then 10.6.7.

    What could be the problem? Memory? Graphics card? OS Update? Hardware? In one of the forums I googled, the mouse cursor still moving is a sign it's not a graphics card problem. Also read that reinstalling does not remove the problem. I also thought that if it was the memory upgrade, we would have kernel panics instead (doesn't happen). I was about to recommend this for service (under AppleCare till 2012) but I thought that it might be hard to replicate the problem unless they use it as we do, 24/7 room temperature with no air-conditioning (already used SMC fan control but it would not raise the CPU fan rpm, only the ODD & HDD responds; CPU temp usually 51-80 degrees C, graphics diode 63-80 degrees C) & with so many browser tabs open (minimum of 10-20 at a time, maximum about 80 tabs). Having this problem happen about once or twice a week might also mean a long time without our unit as techs will burn it in. I also foresee a long debate with AppleCare hotline and incurring a lot of long distance calls expenses (1-800 does not work for us).

    Anyone else has this problem or has googled a solution for this? Is this an OS X Snow Leopard update problem?
     
  2. elbertlo

    elbertlo Member

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    It may be a RAM problem.

    Try putting the old memory back to see if the problem still happens. If so, it may be the CPU, and if not, it's the RAM.
     
  3. macdrive007

    macdrive007 Well-Known Member

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    Thanks elbertlo, will try the original RAM.

    Another symptom onscreen: there would at times be one or two rectangular artifacts the size of a minimized iTunes player, that would be unmovable - at times would be opaque, sometimes would be transparent as if looking through graded eyeglasses (with text/graphics coming from another part of the screen). This will only be gone after a reboot. My instant hunch was to blame the graphics card but yes, the new RAM could possibly be the problem.

    Any other things we could test/try?
     
  4. Salaryman Ryan

    Salaryman Ryan PhilMUG Addict Member

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    Does this unit still enrolled with an AppleCare warranty?
     
  5. macdrive007

    macdrive007 Well-Known Member

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    Yes, till 2012. However, we hope that will be a last recourse after troubleshooting. The unit is used everyday.
     
  6. chizbol

    chizbol Member

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    Try to create another user account and log on to that one. If it does not appear, then a corrupt preference file is the culprit. If its still there, the it probably is the graphics card or ram
     
  7. macdrive007

    macdrive007 Well-Known Member

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    Have reinstalled the original RAM, so far no problems. Still observing.

    For the meantime, on to looking for that RAM upgrade receipt...

    @chizbol: thanks for lending your expertise. Will try your recommendation if the RAM solution does not work.
     
  8. macdrive007

    macdrive007 Well-Known Member

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    It seems it's not a RAM problem. With the original RAM, the flickering & artifact problem came back last night. Had to reboot as the screen froze.

    Will try the new user log on next...
     
  9. essay

    essay Active Member

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    I have the same problem.

    Anyone found solution to this already?

    I experience this when I leave my iMac turned on overnight.

    Screen freezes, even as my cursor still moves, but when I click on an icon application (or any icons, folders, etc), it won't launch.

     
  10. jcruze057

    jcruze057 Member

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    does apple has local service center in metro manila?
     
  11. essay

    essay Active Member

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    Update.

    Looks like my lion update of my iMac has fixed this problem.

    For one week now, I don't experience the flickering and freezing problem.

    Let's see how this goes over time.
     
  12. PESTY

    PESTY New Member

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    I just purchased a used iMac just like yours with the upgrade and lo-and-behold it has the identical problem just as you described in such great detail. So How did your issue end up? Corrected? What needs to be done to get a fix?
     
  13. greta87

    greta87 PhilMUG Addict Member

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    this happened to my iMac before whenever I would scroll down the itunes music store. The iMac would freeze; except the mouse could still be moved but wouldnt be able to click on anything. somehow the problem just went away. I did software updates & reboots. don't really know which one did the trick
     
  14. macdrive007

    macdrive007 Well-Known Member

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    I forgot to update. May be of use to others with the same experience.

    Brought the iMac to apple service center before the APP expired. Tech wasn't able to replicate the problem on site so verdict was there was no problem.

    So I went to the service center and tried to replicate "overheating" by opening about 150+ tabs using safari, Firefox & chrome, opened 30 more apps & windows, and after about 2 hours of overworking the Mac, it froze.

    So my hunch was right, that the GPU was overheating at our room temperature venue, and it was harder to replicate it at the tech center due to airconditioning. Convinced, the tech took pictures of the anomaly & apple replaced the GPU as well as the screen (cloud problems as usual).

    iMac has been working fine ever since. :)
     

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