When I open up Active Directory Users and Computers from my workstation, I receive an error:

Naming information cannot be located because:
Logon failure: unknown user name or bad password.
Contact your system administrator to verify that your domain
is properly configured and is currently online.

If I log in to my workstation as somebody else, it works. If I log into a different workstation using my account, it works.

All the workstations in question are running Windows Vista (32 and 64 bit) or Windows Server 2008. The domain controller in question is running Windows Small Business Server 2008.

Everything else (that I tried) in the Remote Server Administration Tools runs just fine.

Any thoughts?

Edit: I just tried reinstalling RSAT. No such luck.