Got an 8600GT problem, please help!

Hi all, bought an 8600gt a couple of weeks ago and I'm getting a problem in which every now and again while playing a game (even simple games like PKR) it'll flash and crash, I'm at my wits end now and need some advice. I've even tried under-clocking it but as soon as i did this it flashed and crashed . Do you reckon the card is faulty?

Athlon 64X2 5200 (2.60Ghz)
Asus M2V Mainboard
4Gb DDR2 RAM
Standard Realtek HD Sound (any ideas how to get that headphone jack to work by the way?)
500W PSW (12A on a +12V line)
Running Vista 32Bit but did the same when I had XP (only upgraded last week)

Had a feeling it might be the PSW but didn't know, I take it that could REALLY affect it then?

Have got a 420W PSW running at 14A on +12V, but had the same problem with that one.

Uhm, I beg to differ. Look at the amps on the PSU he lists. 12 amps? That's very very low if that figure is right. I mean you can try video drivers and all, but if your PSU is not powerful enough, yes it will lock up. Might be lucky the PSU or card is not burn't out yet. If PSU's go, they can sometimes take more parts with them when they blow. But double check that amperage rating and repost it, just to be safe. Watts don't always mean that much, mostly look how high the amps are on the 12v+ rail.

As much as possible. In my opinion the more amps it's got, the better. Antec makes some decent units. A lot of other guys can recommend others as well. But like antec, corsair, seasonic are said to be good units.

OK cheers guys, will go to ebay right now and get a new PSW, can see a 700W 33A at £23 so that'll do nicely, cheers for the help