I've been looking at a problem on a friends SBS (2003) server where the client PC's aren't able to connect to the server with a variety of errors reported. Checking the server itself the only indicator of an issue is an error 5782:

Dynamic registration or deregistration of one or more DNS records failed with the following error: No DNS servers configured for the local system.

Running a dcdiag reports that there are no DNS records registered for the DC so I fixed the problem by doing a netdiag /fix after which the dcdiag comes back clean and clients are ok again.

It happened a few weeks ago as well and the same fix solved it. What are the possible causes of the DC DNS entries going missing? Is this a config option that needs tweaking or could it be solved by something simple like scheduling the SBS server to re-boot periodically?

The only change they can think of that was made near to the time of the first instance of this problem occurring is that RRAS was started up to allow for a VPN connection from a home user.

NB - The server is setup with a pair of NICs in a team so the server has a single virtual NIC providing both LAN/WAN connections to it. An external hardware firewall is in use rather than the windows firewall.