milkman's Power Supply Problem

Hi, everyone. I'm a first-time system builder and am having a problem with my power supply. I had everything up and running, but on only the second day of using it (so only a few hours of use) my system froze, and now it won't start. The fans will spin, the HDD and DVD-ROM drives will make noises, but the motherboard doesn't beep, and then everything shuts off. It tries again after a few seconds. I was sure the problem was with the PSU because there was a part in the troubleshooting guide that described the problem exactly. I sent it back for a replacement, confident that it was a broken part and not my fault, but I just got the new one and I still have the same problem. So now I'm really frustrated because I've got a huge 1500 dollar paperweight.

The PSU in question is a Thermaltake TR2 500W , which I'm pretty sure is enough to power my system (details below). I have not overclocked my CPU yet and the only thing I changed in BIOS was a +0.1V in DIMM voltage because my ram was rated at 1.9V whereas my mobo default was 1.8V. My system froze once before this, and I thought it might have been because I hadn't changed that.

Mobo = GIGABYTE GA-965P-DS3
CPU = Intel Core 2 Duo E6300
RAM = OCZ Platinum Revision 2 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 Dual Channel
gfx = XFX PVT71PUDP3 GeForce 7900GS (psu has 29A on +12V rails, should be enough)

I also have a sound card and a tv tuner that I've added since the psu went away to be replaced, and of course a HDD and DVD-ROM drive that are inconsequential to this problem. Do you hardware wizards have any idea what's up? Is it possible that I got two faulty[/list] PSUs in a row? Is the problem somewhere else in my system? How could it have worked perfectly for a while and then stop? Could it be related to the RAM being rated higher than the motherboard's default?

Please help!

Why? 1.9 should be enough right? And how would I do that? I can't even get to the BIOS to change it. Should I try clearing CMOS (whatever that is)?

Well I reset CMOS by removing the battery temporarily, and now it's up an running better than ever. It would seem that I never had to send my PSU away at all. It could have also been that my video card was not inserted all the way. Oh well, all is better now!