Need help with Reboot cause

[Peter J. Stieber]

PS = Pete Stieber
PS> This is going to sound vague, but here goes...
PS>
PS> I have a dual opteron system that has been acting
PS> as the worldly node for a small cluster of computers
PS> since September, 2004.  The machine is running the
PS> latest x86_64 Fedora 10 kernel that I recently
PS> loaded (April 2).  The machine reboots without
PS> warning.  I can't find the cause in log files (maybe
PS> I'm not looking in the correct log)...

After trying a "little bit of everything" and learning a lot about 
lm_sensors and hddtemp from those of you that replied, I took a chance 
and bought a replacement MB from Newegg.

I replaced the Tyan Thunder K8W (S2885ANRF) MB with and ASUS K8N-DRE.

I used the same CPUs, memory, and PS and it works.  I don't see anything 
wrong with the MB, but it will be sent to the recycle center.

Thanks for all of the help.

Pete