Video Card problems

[Adamb]

I just bought a brand new system for my wife, it works great, except for one problem, at random times, (could be browsing, idle, or installing something) the screen will just go to the solid color of the background that she is using, applications installs etc still run in the background so i don't belive its locking it up, Anyway I'm stumped. Tried new drivers it didn't help. the card is a Evga GeForce 8800GTS 320MB 320-bit