I would also ask what game you are playing. I have seen problems like that w/ OpenGL Issues (video card), Driver issues, and I have personaly seen screen flicker, and that become unplayable on openGL games, but finally my monitor of all things shut down. I got a new monitor and everything works perfect again.. lol. re-booting games like that can be a LOT of things. including as "jimmy S." said " over heating.. but without knowing what game you are running, or anything about your system. My first thoughts tend to be DirectX version, and drivers. That may or may not be correct, but its the first thing I would look at. To be updated w/ correct drivers for motherboard, video card, sound card, and game patches. I find that solves at least 80% of game problems.