Login error for ONE agent

[Rotyn]

Dear all

I am facing a very strange issue

Facts:
OTRS connected to LDAP, working fine.

Problem: There is ONE agent who can login, doesn't matter what we are doing.

My Appache error log does show this:

[Mon Nov 26 12:35:34 2012] [warn] [client 172.20.1.236] incomplete redirection target of '/otrs/customer.pl' for URI '/' modified to 'https://194.25.158.178/otrs/customer.pl'

Even when I am trying to login as the agent (via "Switch to user" in the Admin interface) I will face the same problem.

Something else I can see: the login attempt as this user fails, but
(a) a session for this user is created (checked in the session management in the admin interface)
(b) but the last login date for the user isn't updated in the database

Does anybody have an idea? I am looking into this problem since 1 week....without success

Kind Regards
Rudy

[crythias]

Why is the agent trying to login to the customer side?