Terminal Serer - Access denied

I am running Windows 2003 Sever with terminal server and
terminal server licensing installed. I gave several people
access to login to the server. They have been able to
login just fine. After about a week I added two more
users. When they attempt to login they get an error
messages saying access is denied. In the event log an
error stating "Logon rejected for MISD\username. Unable to
obtain Terminal Server User Configuation. Error: Access is
denied"

We are currently running an a WindowsNT domain. The server
is part of the domain and all user accounts are
authinticated through the domain.

I don't understand why the server is allowing some users to
login and others not.