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iMac freezing after Mountain Lion Upgrade

After upgrading my iMac to Mountain Lion it is freezing at least one a day. Sometimes the screen get messed up right before getting frozen, something like this video (from another guy), but they move from top to bottom to me.


I never had this problem before, it started right after the Mountain Lion upgrade.


Anyone with the same problem? Any ideas?

iMac, OS X Mountain Lion, Mountain Lion Server installed

Posted on Aug 12, 2012 4:39 AM

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54 replies

Aug 12, 2012 5:40 PM in response to vsserafim

Ok, things are getting worst!!! After sometime working my iMac got in sleep mode. When I got back to work on it the screen was completely black and I'd tried a cold restart. Surprise, surprise: I hear the usual DVD drive sound from the boot and nothing else, just a completely black screen. The iMac is on for sure, cause if I hold the power button for some seconds I can hear it shutting down.


Never had anything like this until I upgraded to Mountain Lion. 😮


Now I really need some help! 😕

Aug 16, 2012 7:32 AM in response to WilfridSellars

Permissions Repair:

Go to applications then to the "other" folder then go to disk utility, on the left hand side you will see a white box. Select the second option, usually called "mac HD" with that selected click on "repair permissions" in the center towards the bottom of the screen. Wait for it to complete, then see if this fixes the issue.



PRAM Reset:

1- Ensure the machine is powered off.

2- Locate the following keys on your keyboard in preparation for Step 4:

‘command’ – ‘option’ – ‘P’ – ‘R’

3- Press the ‘power on’ button.

4- Immediately – and before the grey screen appears – hold down ‘command-option-P-R’ all together.

5- Keep them held down until you’ve heard the start-up chime twice. After you release them you should hear it again, and hopefully your Mac will boot up normally

Aug 16, 2012 8:20 AM in response to vsserafim

I feel your pain. I have the same problem. It started immediately after installing Mountain lion. And I had no problems before that.


I get constant beachballs and stalls. They can happen at any time. I can't play a QuickTime file without freezing every few seconds. The freezes last over a minute. And I get stalls when using the Finder, Safari and Chrome. Sometimes my MacBook Pro won't even boot. The gear below the gray apple just keeps spinning for minutes without ever progressing. And even when my machine boots, the booting is very slow.


I've tried fixing permissions. Booting from a thumb drive and repairing my disk (which it needed.) Reinstalling Mountain Lion from the app store. Nothing helps. I will try resetting PRAM and report back if that helps.


Here's my only possible clue as to what's wrong. The information window for my hard drive shows incorrect information. It shows 639 GB total capacity. That's okay. That is the correct capacity. Then it shows 1 TB available! You can't have 1 TB of space still available on a 640 GB hard drive that is more than half full. I have no idea if this is related to my stall problem.


I'll be watching here for any suggestions. They will be gratefully accepted.

Aug 20, 2012 6:44 AM in response to garethhart

Similar problem here on a 2007 iMac recently upgraded from 10.7 to Mountain Lion. It was not an issue before.


Almost every day now I come back to find my machine 'sleeping' , or so it seems.


But when I try to wake it by mouse movement, I discover a fixed unmoving mouse pointer. Keyboard input doesn't help either. The machine is frozen. I have to shut down the iMac and restart for things to be back to normal.


Let's hope it's something Apple can fix with an update.

Aug 20, 2012 7:29 AM in response to vsserafim

I too am having the Screen issues followed by a freeze. I have had the inability to wake from sleep for the last few weeks also. Running 10.8 on a mac Pro 2008 with 2 quad core 2.8mhz. Just this AM my screen flickered then distorted. Mouse curser would move on screen but could not effectivly quit anything. tried permissions repair, disk repair. reinstall of OS and all failed. Best quess it is related to video drivers somehow.

iMac freezing after Mountain Lion Upgrade

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