Random Network Disconnects

At the place I work we have a number of computers running
Windows XP(mostly Pro), some on our domain(via VPN) and
some at other sites, only networked to another one.

For some reason some of these computers have been
disableing the network connection for no apparent reason.
I have searched the KB, but didnt find anything that
sounded right. I also searched here.

It doesnt happen offten, but when it does happen its a
hassile because it takes some time to diagnose these
problems. Does anyone know of what might be causing this
problem? We use Mcafee Virus Scan, incase that holds a
clue.