Try typing the password again. If this does not work, several things could be happening. The user may be locked out. Solution wait 20 minutes and try again or have a network administrator unlock the account. The user may have forgotten their password.
Solution have network administrator change the password to something new.
The user may not actually have a password but is trying to use one. Solution have user try to login without anything for the password. The userid may be incorrect. Solution - Check both the login and NT tabs of the login window. Solution have network administrator create the userid.