Kerberos working except for one user.

I have a server that is working great Kerberos etc all work like a champ except for this one user. I have verified the issue on multiple machines and can get other user tickets on this machine so I know it is working. Essentially typing in his credentials gets. "Client not found in Kerberos Database." I would just delete the user and get it working, only problem is that this user is an admin and more importantly a diradmin. So long story short is there a way to force this user into the database? Thanks for any help you guys can provide!