Mike has the solution to the DCOM error I encountered after installing WSS with SP1 on Windows 2003;
The error on the event log is like this:
The application-specific permission settings do not grant Local Activation permission for the COM Server application with CLSID {61738644-F196-11D0-9953-00C04FD919C1} to the user <serverName>\mossService SID (S-1-5-21-<serviceSID>). This security permission can be modified using the Component Services administrative tool.
Altug Sahin's Blog 