How to kill a USER.... (maybe a bug?!)

[rembrandt <rembrandt_(_at_)_jpberlin_(_dot_)_de>]

I've a little problem.
How to kill a user if this user has no PID?
All processes of this user are DEAD and KILLED but he's still logged in
(w, who, users).

This error is NOT repeatable but I could tell you how to try to
reproduce it.

I was logged in on my server from the university.
After some minutes there was a network-problem in the university and my
connection was closed.
I logged in today again and my session exist even the PC in the
university was OFF over night.

So I logged in and I've 1 real login and 1 login wihtout ANY process.
FSCK reports no error and the hardware works well.
I rebooted the server course this ghost-login.

Maybe a guy knows what's to do next time.
Even not pls. see it as bugreport, thanks.

My OS is 3.5 stable with all known patches. =)