samba - May 2009 - WinXP user password not accepted - very strange !!!

Dear friends,

I have an Ubuntu 8.04 server fully updated running Samba 3.0.28a. Currently the
ubuntu machine acts as a PDC and all clients have joined the domain successfully
(clients are all WinXP SP2).

The strange thing is only with one user where:
If the user logs in with his password all works well. If he restarts or shutdown
his machine and tries to relogin the system tells him that his username/password
is not correct.
If I reset his password @ Ubuntu with smbpasswd username and renter the exactly
same password, the user logs in successfully!
This is the oddest thing. It appears as if this user's password is
"canceled" every time despite the fact that the user has never changed
his password during this period of time.

Does anyone have any ideas?

All WinXP SP2 clients have requiresignorseal = 0 and they have all joined the
network in the exactly same way. All machines have machine-trust-accounts which
have been created in the exactly same way. All users are working perfectly and
all processes are running smoothly with not a single problem except the before
mentioned.

Your help is greatly appreciated.

Chris

>
> If the user logs in with his password all works well. If he restarts 
> or shutdown his machine and tries to relogin the system tells him that 
> his username/password is not correct.
> If I reset his password @ Ubuntu with smbpasswd username and renter 
> the exactly same password, the user logs in successfully!
> This is the oddest thing. It appears as if this user's password is 
> "canceled" every time despite the fact that the user has never
changed
> his password during this period of time.
>
I once had that problem with one computer. I solved it by unjoining and 
then joining it again to the domain.