Mid-2011 iMac Freezes
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.