Help me!

[fishdbaz]

Ever since I installed my new GeForce 8800 Ultra graphics card a few months ago, my computer's been just fine, however, last night things started screwing up. In the evening I could play games just fine, but later on in the night after an MSN conversation, when I tryed to play one of my games nothing worked! Everytime I try to play a game (any game) it plays just fine for a while, then it starts blacking out and coming back and finally it crashes and a little pop-up says that my display driver stopped responding.

I tried updating to the latest drivers; no good. I've checked the system's core temperature; well within reasonable parameters. What the heck is wrong here?

EDIT; And HL2.net is flickering, ARGH!