Error when Attempting to Logon to a WSBS 2003 Client Computer

When I attempt to logon to a DNS Win SBS 2003 Server from a client computer I get an error meassage which reads as:

The System cannot log you on now because the Domain LTSC is not available, I also get an error message which reads: ‘The System cannot log you on know because the Domain, LTSC, is not available.

I would be grateful if someone has any idea what is the cause of this problem?

Regards
Gerryw (again)