NT logon failure

We change the logon password in our NT server for a remote user. We can test the login successfully. When the remote user attempts to login the system keeps removing the password he entered on his screen and will not allow him to continue. At this point we cannot logon using his id either. We change his password again and run into the same problem. But, we get to a point where the password takes correctly and the user continues with no further problem.
What is causing this and how do wecorrect it?