PNY 6600 timeout probs...help!!!

I recently got a PNY Verto 6600 256mb video card and installed it on my old Gateway.. IT has a 1.5Ghz P4 and 512 SDRAM (PC133). PROBLEM: Occasionaly when i boot up or start a game the monitor will time out and the pc becomes unresponsive to everything except to the ever fatal holding of the power button until it shuts down.
I have downloaded the latest Forceware for it and deleted my old Catalyst using it's uninstall tool so the drivers are updated with no confliction...
I think that it may be the old 150W Powersupply but i could be wrong..any help appreciated.

The minimum requirement for that card is a 300W power supply, so you would be correct. With the older CPU and all you may have gotten away with a 225W or 250W, but 150W is way off. Luckily you can get a 300W very cheap

-Rav