Need someone to diagnose a video card problem?

I bought a HD 4670 1GB several months ago, and its great when it doesnt a) VPU Recover b) Freeze, forcing manual shutdown. It has VPU Recovered occasionally, only when i play graphic intensive games (GTA IV) , though the frequency of it depends on the HD 4670's mood (Very random, very frusturating). Well recently, i started playing APB Reloaded (google it), runs pretty good, with the usual fps drops during close range fx. But this game in particular somehow causes more VPU Resets IN A DAY then the amount i get in a few months. Maybe it just doesnt like it, but anyway, i need help figuring out how to stop these VPU Recovers.

I have Windows XP 32-bit SP3

Antec Earthwatts 380w continuous power ( +12V = 17amp +12V2 = 15amp =12V = 0.8amp)

HIS ICEQ HD Radeon 4670 1GB GDDR3

Latest video drivers and CCC.

Now i know this is either a graphics card or power supply problem, i just dont know which one.

Is the video card faulty? Is the power supply not outputting enough on the 12V rails?