[samba] smbpasswd doesn't work

[Dennis Knies]

On my Samba-server (normal) users aren't abled to change their password.

When they use smbpasswd they are asked to insert the old password, the new 
pasword and to confirm the new password. After the confirmation of the new 
password they receive an error:

machine 127.0.0.1 rejected the password change: Error was : RAP86: The 
specified password is invalid.
Failed to change password for dennis

As root it is possible to change all users passwords.

Does anyone have a solution?

Dennis