I'd think it's the power supply. It has 2 12 volt rails which output 14 and 15 amps. The 15 amp rail (12V2) connects only to the ATX12V connector. Doesn't leave much for everything else. You should try another larger one (500+ watts) of a quality brand. There's a review at Hardware Secrets that'll give you nightmares. Well, maybe not, but it's not good. Here's a link to the conclusions.
http://www.hardwaresecrets.com/article/557/10