We have been running a SQL 2000 SP4 server for the past 4 years without any problems. SQL is running on it's own hardware on top of Windows Server 2003.
Suddenly I noticed that when entering Enterprise Manager and trying to open the local server that I would receive an authentication error. I can still connect to other SQL servers on the network and manage them successfully.
I then removed the local server from Enterprise Manager and tried to add it again, at which point I got the following error "(LOCAL) - Cannot open user default database. Login failed"
(We are using Windows authentication)
I am also unable to manage that specific server from another workstation.
All databases on the server are up and running, but I am unable to manage them at all.
I can't find anything specific to this in the event logs...