nt authority shutdown error, XP

my dell latitude desktop keeps spontaneously shutting down with pop up box that says "system is shutting down due to nt authority shutdown". gives me 60 seconds, then shuts down and restarts. i managed to override the shut down…what is this? updated norton, ran spybot, nothing affects it.

Without further information it is impossible to say. Take a read through this thread and then start a fresh thread in this forum and post accordingly. Please don't forget to include a brief description of your problem, and somebody will be along as soon as.
Helpers look for posts with zero replies which is why you need to start afresh and why i'll lock this one.