Password problems

[Oren Levy]

Something really weird is going on. Users cannot change their password using
smbpasswd. They get this:

Failed to open /etc/secrets.tdb
Old SMB password:
New SMB password:
Retype new SMB password:
machine 127.0.0.1 rejected the password change: Error was : The specified
password is invalid.
Failed to change password for [ ]

I can log in fine
I can change user passwords with root fine
I can share printers
I can share folders

I have two PCs: a server which dual boots Linux and Win2k server and a
client which dual boots Win98SE and Win2k pro. Samba is the PDC and the
client PC has been added to the domain. Any idea what the problem is?