Sorry, forgot my full specs:

Asus A8N-VM-CSM w/ integrated nvidia GeForce 6150
1.25gb PC 2100
Socket 939 Athlon 64 3200+ 2.2ghz
400w Ultra PSU (crappy gray, stock, came with case.)
Sony DVD+-RW
120gb Seagate 7200rpm hdd
SoundBlaster LIVE! audio
Stock cooling
1x120mm Fan exhaust in rear
Black Ultra Wizard case w/400w PSU

I'm almost positive it's the PSU. Also, I plugged the adapter into 2 molex on the same string. I think that may be it as well, but they're all I've got.

And if it's the PSU, any recommendations on the wattage I should get next, or brand and model?

Thanks again,
Jonathan