Server 2003 keeps dropping passwords

Here is the situation:

Server 2003 with AD running, all the latest patches installed.

We have 1 user who almost every day cannot get logged into the domain. We have reset his password several times, it is set not to expire, no login hour restrictions, nothing we can find that would cause this issue. It only happens with 1 user.

Anybody have any clue as to why this would be occurring??

Oh and no he is not forgetting his pw.