Constant error message on vista

amd phenom ii x4 920
asus m3a78-t
4gb ddr2 1066
evga gtx 260
bfg 50w psu



my temps are fine for all that ask.

i have windows vista ultimate x64 and i want to play cod5 on multiplayer but about 20min through i get a message that says call of duty world at war multiplayer has encountered a problem and needs to close. other people tell me to change my sound setting to 24bit 48000hz but it is already set to that. i had xp before and i could play fine but i suddenly cant play.

what do i do.