System Backups and Abrupt Shutdowns of Server

Hello people,

My question is regarding back-ups and Volume shadow copy service.

Every night at scheduled time, the back-up tasks are executed on my Server 2003 DC (20 XP Clients), and usually after 30-45 minutes when the back-ups are over, the server shuts downs with no logs.

Then next day, I start the server and the system log tells me of event id as 6008 (well, next to vague).

I have checked the possible reasons that I could gather thru the events that happened just before the shut down but not of much use to this problem.

Your opinion n experiences are welcome.

Thanks.