This could be your GPU overheating and somehow. Doesnt go black in some games? Try playing crysis for just a bit longer and i bet it will.
Download "speedfan" and tell us what temperature your cpu and gpu are chillin at.
It only crashes on Warcraft 3 and Civ 4 so far. Havent experienced black screens with crysis and left for dead and red alert 3. I downloaded speedfan and everything is cool except for Temp3 (which I have no idea of what peripheral that is) in 79 farenheit. this is my gpu...http://www.newegg.com/Product/Product.aspx?Item=N82E16814161309