Services keep stopping

I there, here is my problem:
I'm running win2003 Sp2 domain controlers, AD is in windows 2000 native, i
have aprox. 12 DC's in one domain.

Since a week ago, i have some strange behavior on my servers, some services,
such as "worstation, server, windows audio..."
keep stopping and showing no reason on the event viewer.

I've run full anti-virus scan, it detect nothing.

The services stop, i start them and sometime later (like an hour or two)
they stop again.

Anyone has some tip?

Thanks