account lockout

I have a user account that keeps getting locked out even though the correct password is entered. The workstation is windows 2000 with sp1 and it belongs to an NT domain. After the user complains that they’re unable to logon, i check the user account on the PDC and the account locked out checkbox is checked. After resetting the account, the first logon attempt is successful, but subsequent logons are not. The account once again get locked out. Does the domain user account also have to have a matching local account? Any suggestions?