Mid-2011 iMac Freezes

[Fausty82]

I am pulling my hair out trying to resolve a problem with my wife's 21" iMac (mid-2011 model, MC309LL). This thing runs fine for hours/days/weeks but randomly just locks up. Nothing on the system works except that I can continue to move the mouse pointer. However, keyboard and mouse buttons are totally non-functional.

It currently has 4 x 4GB sticks of Corsair DDR3-1333 RAM. I suspected the RAM initially, but swapped it out with identical sticks in my MBP (2011 i7)... and the MBP runs like a top... nary an issue or glitch with either set of RAM. However the iMac continues to randomly lock up and freeze regardless of which set of RAM in installed... so I don't think it's the RAM that's causing the issues.

I am not running any software on the iMac that I don't run on my MBP, and again, absolutely no problems or hints of a problem on the MBP. I've verified all software updates are in place... and spent most of today wiping and reinstalling everything (OS X Lion 10.7.4)... and tonight it's already locked up twice. The only way to recover from this lock up is to hold the power button to turn it off. Then restart in safe mode and, finally, once it's completely up in safe mode, restart into normal mode.

At one point this iMac was in the Apple repair shop for 2 days +, and they reported no problems...

Does anybody have any ideas about how to identify and resolve this issue? I had my wife totally sold on Apple computers until the lockups started happening... now my butt's in a sling, if you know what I mean.

 

[CG68]

Try taking a look at this forum thread. It seems others have had similar problems. Hopefully you might find the answer you're looking for:

https://discussions.apple.com/thread/3194165?start=0&tstart=0

 

[Fausty82]

Try taking a look at this forum thread. It seems others have had similar problems. Hopefully you might find the answer you're looking for:

https://discussions.apple.com/thread/3194165?start=0&tstart=0

Wow... 122 pages in that thread... thanks... will go through it and see what I can find. So far (page 1) a lot of folks talk about video freezing... that's not the case for us... we watch very little video... but it looks like a good place to start.

 

[CG68]

Hopefully you won't have to get to page 122 to figure out what the issue is!

 

[Fausty82]

It appears that the issue is the memory. For some reason the iMac doesn't like 16GB of the Corsair (or Crucial) memory. That memory ran fine in my MacBook Pro, but for some reason, filling the iMac up with it caused the random lock up. I did find forum posts of others with the same issue.

While I can't provide anything more than anecdotal evidence, it's been almost 2 days and we've experienced no lockups since replacing 2 of the 4GB sticks with the original Samsung 2GB sticks... running now with 12GB which, in reality, is plenty of RAM.

 

[Fausty82]

Ok, that was short-lived. The iMac is now at the Apple store... hopefully on the bench right now being diagnosed.

 

[holeout]

Do you happen to run Google Chrome? My Mac Mini was doing the same thing and the only pattern I could find was that I often leave Chrome pages up so I remember to look at them later (some times for days). Once I started shutting Chrome down and not leaving it running for days, freezing seemed to go away.

 

[Fausty82]

Do you happen to run Google Chrome? My Mac Mini was doing the same thing and the only pattern I could find was that I often leave Chrome pages up so I remember to look at them later (some times for days). Once I started shutting Chrome down and not leaving it running for days, freezing seemed to go away.

Thanks for the tip... yeah, the wife runs safari. firefox and chrome... but it's not consistently locking up with any specific software program... just random lock ups... sometime in safari, sometimes in mail, sometimes playing a game, sometimes in chrome, etc...

And there is no software installed on that iMac that is not installed (and that I run) on my MBP... not a single instance of locking up with the MBP...

It's sitting on a tech bench at the local Apple store as I type this... hopefully getting better.

 

[Fausty82]

Apple just called... they found a faulty video card... and are replacing it. Hopefully, that's the solution that we're looking for.

 

[Fausty82]

It looks like a bad graphics card was the issue. It's been running for over 24 hours without a single glitch.

That's the second iMac of that model/vintage that I know of with the same issue... but mine is fixed, so I am happy, because my wife is happy.

If Mamma ain't happy, ain't nobody happy.