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iMac Freezes Up

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CameraCarl

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I have a four year-old 2.8 GHz Intel Core 2 Duo with 6GB RAM running v. 10.6.8 Snow Leopard. For the past two years, I have been getting intermittent computer freezes. One of three things happen:

(1) the screen freezes and the clock stops counting seconds, but I cans till see the desktop and open window. I can still move the cursor but nothing works, I can't use CMD/OPT/ESC or any other keys.

(2) the screen goes completely light grey and none of the keys do anything

(3) the screen gets a vertial corduroy series of lines that are alternating shades of light and medium grey, and again the keys don't do anything

The only way I can get out of this is to manually shut down with the power button and reboot. These events don't seem to happen with any particular combination of actions running on the computer. Sometimes, when I am working in Lightroom with a couple of web browsers open, sometimes with LR idle in the background when I am browsing the web (typically using Google Chrome), sometimes when only LR is open, and sometimes when only web browsers are open. Back when I still had Apple Care, they tried to diagnose the problem but couldn't find any problem with the computer, even after keeping it for a week and running tests. Their solution was to reload the operating system and then reinstalling all the software from scratch. This seemed to work for about a year, but the problem is coming back. I'm starting to get freezes once a week or so. I'm reluctant to have to reload everything. And I'm equally reluctant to buy a new computer as the new iMacs don't have some of the things I need (like a disc drive).

Anyone have any ideas what the problem/fix might be?
 
CameraCarl said:
CameraCarl wrote:

I have a four year-old 2.8 GHz Intel Core 2 Duo with 6GB RAM running v. 10.6.8 Snow Leopard. For the past two years, I have been getting intermittent computer freezes. One of three things happen:

(1) the screen freezes and the clock stops counting seconds, but I cans till see the desktop and open window. I can still move the cursor but nothing works, I can't use CMD/OPT/ESC or any other keys.

(2) the screen goes completely light grey and none of the keys do anything

(3) the screen gets a vertial corduroy series of lines that are alternating shades of light and medium grey, and again the keys don't do anything

The only way I can get out of this is to manually shut down with the power button and reboot. These events don't seem to happen with any particular combination of actions running on the computer. Sometimes, when I am working in Lightroom with a couple of web browsers open, sometimes with LR idle in the background when I am browsing the web (typically using Google Chrome), sometimes when only LR is open, and sometimes when only web browsers are open. Back when I still had Apple Care, they tried to diagnose the problem but couldn't find any problem with the computer, even after keeping it for a week and running tests. Their solution was to reload the operating system and then reinstalling all the software from scratch. This seemed to work for about a year, but the problem is coming back. I'm starting to get freezes once a week or so. I'm reluctant to have to reload everything. And I'm equally reluctant to buy a new computer as the new iMacs don't have some of the things I need (like a disc drive).

Anyone have any ideas what the problem/fix might be?
Click to expand...
Usually random freezes are hardware related (sometimes that is easy to diagnose by changing a problematic RAM stick but if it is something that cannot be easily changed out for testing, ie, essentially RAM or HDD on an iMac this can be difficult to impossible to diagnose).

But if a re-install really helped, just try to re-install the OS again. If you don't explicitly erase the HDD before, all your applications and data should persist (but create a clone or a TM backup, though I prefer a clone for this, before you do this). Alternatively, you could also wipe the HDD and use Migration/Setup Assistant to restore everything very easily from a backup (if you have some reservations against this, test this re-installation over an existing OS on clone first).
 
Try running a permissions repair and disk repair with Disk Utility application. Also try re-seating your ram memory. If that doesn't help, try re-installing OS-X like what Apple did for you last time. Backup all your data to an external drive first with time machine so you can recover your files.
 
I had an unusual situation where the computer did not register input or wake up properly from the lock screen. Quite by accident I discovered my USB hub and/or its cable were the cause. switched them out, no more weird behavior. Not saying this is the same as your problem, but you never know where the weak link could be. So, maybe try taking the computer down to just the bare essentials in terms of peripherals.
 
I had a similar problem after upgrading to Mountain Lion. I followed numerous suggestions that I found here and in the apple discussions forums. Nothing worked until I swapped out my 2-button Logitech mouse for the original iMac mouse. Too soon to say success but it's been 3 days w/o a freeze. good luck
 
Thanks to all. I repaired permissions and verified that the Mac HD and any external drive that was connected at the time of the freeze were okay. I switched to a different USB hub and reinstalled my memory. I don't think it is the mouse since I had been using two different mice at various times when the computer froze. Now, I'll wait and see if the problem recurs before trying to reinstall the operating system.
 
Well the iMac froze up again today. I'll give Applejack a try. Then I'll try reloading the operating system (ugh!). If all else fails, it is time to shop for a Windows PC.
 
Just so no one is as uninformed as I am.... I got desperate so I decided to reinstall OSX, thinking that I ought to be able to archive my files and software. What I failed to realize is that I had Snow Leopard installed but did the re-installation with the original OS disc. Oops. Now I'm installing Snow Leopard and praying that I can recover everything from Time Machine. That is what happens when a non-computer geek tries to do something "simple."
 
You wouldn't have an ATI graphics card in that machine, would you? I have an early 2008 iMac with the ATI 2600 card and had these same problems for over a year. These issues with the graphics card driver kexts in Snow Leopard have been highly discussed on the Apple Community Forum boards and the Mac Rumors boards for quite a while.

Check this thread out when you have some time.

Loading…

forums.macrumors.com

The kext replacement with older kexts solved the problem with mine. I was having the same symptoms as you described, sometimes 3 and 4 times a day. Since replacing the kexts I haven't had a single crash in 9 months.

Here's a link to the guy's website who figured this out and posted a fix.

Loading…

blog.krzysztof-turek.com
 
I did reseat my RAM a couple of times; even switching the location of the sticks (or whatever they are called by folks more tech savvy than me).
 
Mike, Thanks! This is the first (!) time anyone has identified similar problems to mine; and I've been to the Apple Store at least twice and called Apple Care too many times to remember about this. So it is nice to hear my problem is not unique. I have to decide if I want to try the kext fix proposed. I'm not competent when it comes to computer stuff and it appears that some folks have kernal failures when attempting the fix. With my luck, this will happen to me too. But thanks for the help. It is at least reassuring that this is a recognized problem even if Apple is doing nothing to fix it.
 
The kext fix is VERY easy and mine worked the first time I tried. Just make a Time Machine backup (or a clone if you have Carbon Copy Cloner or other cloning software) and let it rip! My user experience has improved dramatically. I was ready to tear my hair out before finding this fix.
 
Thanks again. I've decided to give it a try if I get a freeze again. I just worry that about half of the comments on Krzystof Tureks webpage were from users who suffered a kernel failure when they tried the fix, and I have no idea how to recover from this. I guess I can google it before I try the repair.
 
Another thing to try is to re-set the PRAM and the SMU module. Easy to do - Start the computer while holding down the command+option+P+R keys. the computer will start with the normal chimes and as you are still holding down the keys, will restart with the chimes. Let the keys up and start normally. This re-sets the PRAM. Re-setting the SMU is similar but has more steps. Here is the site giving the sequence:

Loading…

support.apple.com

When I did this, the computer was a bit more responsive and quicker. Can't hurt.

Will
 
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Thanks, but I've done that numerous times and it doesn't seem to help. I think the problem is most likely the video driver issue identified a few posts above. I shall try that fix if my problem recurs. I just reloaded the operating system and am hoping that will help for a little while yet. Meanwhile, I'm starting to research PCs if I need to buy a new machine. This one has been nothing but one problem after another ever since I got it (replaced the hard drive, replaced the logic board, new bezel, replaced memory; but I sure got my money worth out of Apple Care. Unfortunately I never could convince them to give me a new machine.)
 
CameraCarl said:
CameraCarl wrote:

Thanks, but I've done that numerous times and it doesn't seem to help. I think the problem is most likely the video driver issue identified a few posts above. I shall try that fix if my problem recurs. I just reloaded the operating system and am hoping that will help for a little while yet. Meanwhile, I'm starting to research PCs if I need to buy a new machine. This one has been nothing but one problem after another ever since I got it (replaced the hard drive, replaced the logic board, new bezel, replaced memory; but I sure got my money worth out of Apple Care. Unfortunately I never could convince them to give me a new machine.)
Click to expand...
Sounds like you bought a Lemon instead of an Apple.
 
Hello again. I am reopening this thread because I upgraded my iMac to Mavericks and apparently the old ATI Radeon problem is back again. I had done the kext fix on it when running Snow Leopard and everything was fine until a couple of weeks after doing the OS 10.9 upgrade. The great instructions for the kext fix that were recommended to me apparently won't work with 10.9 and the newer posts about fixes on the internet are not nearly as clear regarding what to do. Has anyone found a set of instructions as clear as those of KrzysiuTurek for 10.9?
 
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