Only 1 computer denied access to DC

I have about 60 workstations in a WinServer2003R2 Active Directory network.
All are fine with the exception of one. On this single computer, even though
the user can logon to the domain and access most of the network objects,
(shares, printers, etc.), just fine, when trying to access a particular
domain controller, it asks for logon credentials, and no matter what
credentials are entered, (full domain admin, etc.), this particular computer
always receives "Access Denied". No other computers have this problem.

I suspect it may be a particular Service that's either started or stopped on
this computer, but can't figure out which one is responsible. Or could it be
some other security setting? Again - it's workstation specific, regardless
of the logon at that computer. All others are fine.

Thanks for any ideas or suggestions.

John