[Samba] Password change from win client doesn't work

[office at office-sis.dyndns.org]

Hi.

If a domain user wants to change his domain password from the windows
client, the client pc gets inaccessible for long time. After this time a
popup appears with a message like this:

Your password could not be changed. The DOMAIN is not available.

In the samba logs I get this message:

 hg-k2 (192.168.0.15) couldn't find service "USERNAME"

According to the example smb.conf on samba.org I have this lines in my
smb.conf:

passwd program = /usr/bin/passwd %u
passwd chat = *New*Password* %n\n*Re-enter*new*password* %n\n
*Password*changed*

Thx

Josef