although I doubt the 9600 or 9600 pro have temperature sensors, you can try downloading a temp monitoring program and see if your chip is overheating..
also, shutdown your comp, take out the psu plug, take out the vid card and pput it back in, make sure you hear the snap sound..
also, does this problem happen with every game/program you run?
_P4 Northwood 2.8C Ghz HT
_Kingston 512 DDR400 Ram [2x 256]
_Awesome looking white plain case with cool green and red power/HD lights, and a newely acquired Intel P4 sticker!