Groovy man; psychedelic. Since this is in the screenshots section are you just sharing? Or are you asking for help to fix it?
If the latter then, well it doesn't really look like overheating, that usually causes random artifacts. Like Dynadude up there said it looks like you're not rendering the game's textures. Could be a game bug though, did it just happen that once or is it a persistent problem?
If it's not going away then update your driver, but do it properly in case there's something corrupt in there. By properly I mean don't just install the new on top of the old; remove the old driver first through add/remove programs and run some sort of cleaner,
ccleaner is a decent free one I think, to get all the bits n pieces out. Then install the new driver. I was taught to always do this when you update drivers anyway, but I don't think most people do.
If that doesn't work, then open up the case, insert a live hand grenade with the pin removed and
quickly close the case and exit the immediate area.