funny, ehr, or no funny at all...
i can agree that it might be your power supply. i played a singleplayer mission the other day and when one of the alien ships shot its laser in my face, the screen was completely white. my pc restarted instantly after this. i also have some other issues related to my power supply so i guess the crash also had something to do with it.
btw. high wattage or what ever you call it in english is not always better. there are some decent 450watt power supplies out there that are better that some 650watt power supplies.
for 450 watts you should at least spend 50 euros, or whatever currency your country has.

i think its something around 40us $, maybe 35, something like that.
i probably buy this one in the next couple of days:
Super Flower Golden Green Pro 450W