I currently own a 8800gt and happily play cod4 on max, battlefield bad company on medium and a handful of other games which came out within 3 years on max-medium max with reasonable fps. But on some games like eg Crysis, I play in on medium-low fine, i get around 40fps but all of a sudden within 10 mins of gameplay the screen freezes and vertical green lines appear all over. Windows locks up I cant ctrl-alt-del, nothing. Same thing with Mass effect 2, Arma 2, Just cause 2 and some more I currently cant remember. The newest addition being Star Craft 2 which locks up within 10 seconds of gameplay. Sometimes the computer even crashes when the game is paused or in the menu!(Star Craft 2 included) My specs are i7 920, 8800gt and 6gb ram. My case is well cooled and the gfx card fan works fine.
Please help me with this problem, if anyone has had the same thing. I know I should get a new gfx card as the 8800gt is dated but for now my budget is low.
Here is a pic of Starcraft 2 with the crash: