After installing an extra CPU to a DELL Power Edge 1800 server it reboots when the work load is low. It is a Terminal Server in application mode. When there are many users connected and the work load is high it never reboots. The problem happens mostly in the nights, from 8:00PM to 6:00AM, not in working hours, but sometimes it reboots when there are only a few users connected.
After the installation of the new extra CPU we installed W2003 SP2 but that did not solve the problem. The reboot does not seem to be from a hardware failure, but launched by the OS, because it writes something to the event log.
I attached here the errors in the event log. Also an everest report of the hardware.