Error on screen:

HyperTransport error caused a system reset Embedded I/O Bridge Device 2

SEL will show:

Chipset Err: Critical Event Sensor PCI Err (BUS 0 Device 7 Function 0) was asserted

There is a discussion about it here (with no real solution):
http://en.community.dell.com/support-forums/servers/f/946/t/19281276.aspx

I replaced both power supplies with known good units from a Dell 2950. No effect.

My SEL was filled with these errors and, obviously, my server was rebooting frequently.

I noticed NO similarities or triggers. OS did not matter, CPU load did not matter, disk activity did not matter, etc etc.

THE SOLUTION THAT FIXED THIS ISSUE WAS A REPLACEMENT MOTHERBOARD FROM DELL.   THE ORIGINAL DESIGN IS CURSED.

If you have been searching around for the proper ISOs to use.

These two ISOs are what you need to use.

This is bootable:
cdu_1.5_core_225_A00.iso

After you have burned and booted with the above CD.

Download these three files:

http://ftp.us.dell.com/sysman/OM_6.2.0_SUU_A01.iso.001
http://ftp.us.dell.com/sysman/OM_6.2.0_SUU_A01.iso.002
http://ftp.us.dell.com/sysman/OM_6.2.0_SUU_A01.iso.003

The above files need to be joined:

Windows: copy /b OM* OM_610_SUU_A01.iso
Linux: cat OM* > OM_610_SUU_A01.iso

Burn the resulting ISO file.

Boot from the first DVD and then select Update Firmware. Insert Second CD.