while playing any game for several rounds (circa 1.5Hrs) the screen freezes and there are blotches of color. after resisting the urge to gnaw through the keyboard cord and send it through the LCD. I eventually restart the computer. Also I need to repair windows every few days. I've run a memtest for 2-2.5 hours and no errors happen. All the while the nominal temp is 61C. When I run 3dmark05 there are no artifacts. the card is a xfx6800nu unoverclocked running on omega drivers. The MOBO is a chaintech VNF3-250, there are two sticks of corsair PC3200 LL. As well as an unoverclocked s754 2800+ . Could there be some benchmark to test the video card memory alone?