HELP! My computer keeps randomly shutting down!

[SparkyJJO]

I put my new opteron 165 in my Asus A8R32-MVP board, and started overclocking. Now I'm used to when a CPU is unstable when overclocking the system will hang or reboot or BSOD. But this has me perplexed, I've never had my computer just randomly shut off before. It is almost like someone flipped off the PSU switch. It has done it a couple times to me yesterday, then today several times and it is really random.

Full specs:

Asus A8R32-MVP
Opteron 165 CCBBE 0617 FPMW, IHS-less (currently at 2.8GHz, trying to find the sweet spot between speed and temps)
G.Skill 2GB PC3200 2.5-3-3-6 1T @ 156MHz (having memory divider issues)
Radeon X1900XT
Antec Truepower II 550W PSU (6 months old) Antec link

coretemp hits but doesn't go over 54 degrees C on core #1, core #0 is the cooler one but always the first to fail anyway.
I previously tested the PSU with a DMM a few months back to check how stable the rails were and they were all spot-on.


I tried swapping the PCIe connectors on my X1900 to see if maybe I had a rail overloaded but that didn't help anything.

Any ideas?

 

[coupland]

It's almost certainly overheating. My machine had a problem where the CPU fan wasn't quite placed properly and when the system detected the CPU temp exceed a threshold it would do a hard shutdown, like someone flipped off the PSU switch. Re-seated the fan properly, no more shutdowns.

 

[SparkyJJO]

I thought that but then it was running at higher temperatures before I removed the IHS and now the temps are a few degrees lower....