Some 2011 MacBook Pros Experiencing GPU Glitches, System Crashes
It appears that the MacBooks, first released on February 28, 2011, are displaying screen glitches primarily during graphics-intensive work or games. MacBook owners have noted visible striations and image distortion or an entirely blank screen, which can often be temporarily fixed with a reboot.
Along with graphical issues, MacBook Pro owners are also seeing frequent reboots to a gray screen. Apple has several suggestions for customers seeing a gray screen, including booting into safe mode and reinstalling OS X, which has not managed to solve the problem for MacBook Pro owners experiencing issues.
Apple has done logic board replacements in some cases for affected users, but reports indicate that the issue has reoccured after a logic board replacement as well. It is unclear why the MacBook Pros are experiencing problems, but Apple forum users have speculated that it could be heat related.
The issue appears to affect 15 and 17-inch MacBook Pros that have discrete graphics cards. All of the 2011 MacBooks use AMD cards, including the AMD Radeon HD 6490M, the AMD Radeon HD 6750M (both 512MB/1GB variants) and the AMD Radeon HD 6770M.
Mid–2011 iMacs with AMD Radeon HD 6970 graphics cards experienced similar failures and in August of 2013, Apple initiated a Graphics Card Replacement Program for the computers, replacing the graphics cards of affected iMacs at no cost.