Win 98 password changes - Help!

[Ian Harris]

We've got Samba 2.0.6 running as a PDC, Windows 98 clients domain logins.

Works beautifully except for changing password - when changing passwords
through Control Panel | Passwords, Win98 says 'Unable to change password for
Microsoft Networking because of the following error: Incorrect password'.
As it happens, the supplied password is correct. smbd log as follows :

[2000/03/13 12:50:34, 0] smbd/chgpasswd.c:check_oem_password(699)
  check_oem_password: incorrect password length (-1423948563).

Any clues?

regards
Ian.