I have recently reinstalled Windows 7 and my computer screen just randomly turns black, my monitor says "out of range" and then "No signal", and then it just restarts itself. This has happened 3 times in the last 2 days and blue screen view says its due to Atikmpag.sys dxgkrnl.sys, and dxgmms1.sys. What is wrong with my video card or computer? I have an ATI HD Radeon 4850, with catalyst drivers 12.1 not 12.2 or 12.3 because these are more stable. I will attach mini dump files.