NT4 server logging onto Active Directory domain (Server 2003)

We have an issue where when we log on as the administrator on one of our servers, which is the only NT4 server we still have, it logs an entry in the Event Viewer of the Domain controller (Server 2003) stating the administrator account is locked out, even though it isn’t. The passwords are the same and are not entered incorrectly. This occurs whether we use domain admin or local admin accounts on the NT4 server. Is this a bug with Microsoft with authentication between NT4 and Active Directory? Is there any work around?

Thanks