Some users of early 2009 iMacs who have upgraded to OS X Snow Leopard or higher are still reporting issues with a kernel issue that seems to be due to the Nvidia GeForce GT 130 graphics card that came with the machine, with nary a response from Apple proper. There’s a thread on Apple’s support discussion pages that is now around a year old that mentions the problem. According to the posters there, there was a faulty kernel extension released in one of the later Snow Leopard updates that can cause graphics glitches and even kernel panics when there’s a heavy load on the video card, like when playing games. Apple has not yet responded in the official forums.
What makes the complaint perhaps more intense is the fact that the issue does not appear when using Boot Camp to run Windows and run the very same games, pointing to an OS X deficiency rather than an actual graphics card issue.
The issue persists even with the current version of OS X, Mountain Lion. Some users report that even when they get their graphics card replaced, the problem continues to appear, while others have found that using third-party fan control apps can help keep the cards cooler, thereby keeping the crashes to a minimum.
While both MacNN and TUAW report that there may be hope with an upcoming OS X update that has undergone many revisions, with the graphics system one focus of testing, for owners of affected iMacs, a resolution that might be coming isn’t too reassuring. I’d like to echo these sites’ call for all users who are experiencing this problem to head over to the support thread and add a post to help give the problem some weight, and perhaps get a more official Apple response, including, perhaps, a fix for the issue at no cost.
Source: Apple Discussion Forums