AD Users unable to change passwords

We have been unsuccessful in getting Macintosh users who authenticate against Active Directory to change their passwords. When they attempt to do this either via System Preferences or the Kerberos application they get an error saying the password could not be changed and please see the administrator. All Mac clients are 10.4.6, the servers are Windows 2003 which are fully patched. We have turned off all the password restrictions such as min password length etc.

Windows clients using the same accounts can change their passwords.

Any suggestions would be appreciated.

Thanks in Advance