Is this a PSU problem?

[reichter]

A couple of days ago I just finished building my new PC. I left it on last night to test for stability and when I woke up I found it completely shut down. Since then it has shut down twice. Once while I was just reading some website and a third time a few minutes ago right after I had run 3dmark06. The motherboard beeps and everything powers down. My setup is as follows:

Asus premium SLi
AMD 64 3200
1 gig corsair xms
Rosewill rp500 psu

I have checked temperatures and the cpu is at 32-34 while the mobo is a little warmer at around 38. Haven't OC'd anything yet.
I thought it was a good quality PSU but I really can't think what else could be causing these annoying shut downs. Last night I did replace my stock fan with a Freezer 64 Pro but I can't imagine this could be the cause, right?
Another thought I just had was the surge strip I'm using. It's several years old and I have the monitor and 3 other minor gadgets (modem, router) plugged into it along with my PC. Could the PSU simply not be recieving enough current?

Edit. When I installed the new fan/heatsink I used some 2 year old OCZ ultra 5+ thermal compound. I'm assuming this isn't an issue since my cpu temps are pretty low.

 

[jackschmittusa]

mb temp? Is it the ambient temp? And how could it be higher than the cpu on air? Are you pulling power from the mb for the hsf?

 

[reichter]

Originally posted by: jackschmittusa
mb temp? Is it the ambient temp? And how could it be higher than the cpu on air? Are you pulling power from the mb for the hsf?

I got those temps using PC Probe II which came with my mobo. I just checked the temps in bios and the CPU is at 29 while the mobo is sitting at 37. I'm no computer guru so I wasn't sure if this was normal or not. Apparently it's not. The mobo temo rose 4-5 degrees when I installed my new fan which seems odd. Maybe it's a problem with the fan after all. Didn't have these issues with the stock fan but then again I haven't been running this rig long enough to be 100% certain.