samba - May 2004 - Unable to add Windows 2K/XP Pro clients to Samba domain

I have Samba 3.0.2 working with OpenLDAP (ldapsam) as backend except I
can only use Samba as a workgroup not as a domain. Because of the added
security of domain membership, I would like to add all clients as
members of the Samba domain.

When I first add the Windows client, I receive a message returned
stating

The following error occurred attempting to join the domain "MYDOMAIN":
The username could not be found.

Checking the ldap database immediately afterward, an entry was added for
the client (add machine script used in smb.conf) but the client was not
added to the domain. If I again attempt to add the Windows client I
receive the message

The following error occurred attempting to join the domain "MYDOMAIN":
No mapping between account names and security IDs was done.

though this error obviously has something to do with an entry being
found but the client isn't able to use it properly.

I have disabled several local security policies relating to signing and
encrypting communication with a server but it doesn't seem to have done
anything.

Would anybody have an idea where I may be going wrong? If you need more
info, please let me know.

Thanks,
Patrick