SB Server 2003 Problems

SB Server 2003 is the the Domain Controller on small LAN. Was working fine
up until Monday. Now, I can ping all nodes from the server and I can ping
the server from the nodes, but I can't log on to the domain and access the
shared files on the server from ANY of the nodes. I've looked at the event
logger and one of the error messages that is in there (starting yesterday)
is:

"The DNS server was unable to open zone MainSystemR.local in the Active
Directory from the application directory partition
DomainDnsZones.MainSystemR.local. This DNS server is configured to obtain
and use information from the directory for this zone and is unable to load
the zone without it. Check that the Active Directory is functioning properly
and reload the zone. The event data is the error code."

I took a look at the MS knowledge base, but couldn't find anything that
seemed to address this. Any ideas?

Ther was no software installed, or anything else that might have brought
this on (well, other that a botched effort to set it up as a VPN server,
although it worked fine for a couple of days after that, as well.

Could this be causing it? If so, is there a way to go back and clean up
everything that had to do with the VPN installation attempt?



Tim