Why does my Intel motherboard sometimes spontaneously power off and back on again?

An issue has been identified that in certain hardware or software configurations, systems using the motherboards listed below will appear to power off and then back on again. This behavior may occur every hour as if on a schedule. It may also occur for days at a time and mysterious stop for a period of weeks, and then mysteriously return. Other improvements are sleep related and long delays in booting. See the release notes for more information.

Most of our users who apply the BIOS update for this motherboard linked below see these behaviors disappear.

DPP3510J.86A.0437.EB.EXE Size: 6318Kb; Date: 5/11/2008 (release notes)

Updates Intel DP35DP, DG33BU, DG33FB, DG33TL to version 0437.
Enter the BIOS on the first reboot (only as needed) to enable RAID, change boot order, disable onboard audio, etc.

NOTE: Do not allow the flashing process to be interrupted.