Can video card problems be PSU problems?

Okay, I bought a Gateway desktop QUITE some time ago, and it came with a (then state of the art) nVidia GeForce 4200 graphics card plugged into a PCI slot. I upgraded last year to an nVidia GeForce 6200, and ever since I've been having problems. Video games I try to play will crash and freeze on me, and it's annoying me. Theoretically, the card should be able to handle those games (BioShock and Stalker), although at minimum graphics levels.

I calclulated peak power usage on my system (using an onling calulator for the estimate) at 280 watts. I cracked my computer case last night, and found that I have a 250W power supply. Could this be causing my problems? Could the games I play require additional power usage that my PSU can't supply, and therefore it crashes the game?

this may be the problem try getting new psu!!!

like a 350w psu