Server rebooting itself

[Don O'Neil]

I have a 6.1 machine (AMD X2-5200) that reboots itself from time to time for
no apparent reason. Today, I caught it in a reboot and on the console it
said it was shutting down the CPU's, like someone had hit control-alt-delete
on it (the same message)... But there is no keyboard attached to it, and
nobody was logged in.

This happens randomly every 3-20 days (no apparent pattern). 

I originally thought it was the 3ware controller causing it, but there was
no correlation.

I tried installing 'mbmon' port, but when I run mbmon -d I get:

mbmon -d
InitMBInfo: Operation not permitted
This program needs "setuid root"!!

The SUID flag is set, and I'm running it from root. I am wondering if there
is a possible power supply issue, or something like that. I swapped the PS
some time ago for a bigger one, but that didn't change anything. If anyone
has any suggestions on how to get mbmon to work I'd love to hear them. The
MB is GIGABYTE GA-M61P-S3 GF6100 AM2, which uses the nforce4 chipset. I'm
not even sure if mbmon works with that newer chipset or not.

I'm suspecting power problems further upstream (at the data center) but I
have no way of knowing. There doesn't seem to be any coorelation with usage
either, so I'm kind of stumped.

Any suggestions on what to check next?