[Samba] Unable to join domain using ldap backend

[MONGAN, DAVID (JSC-DV2) (USA)]

net rpc join

Create of workstation account failed
User specified does not have administrator privileges
Unable to join domain BOB


I'm logged in as root.
I setup ldap using the Idealx instructions and latest scripts.
I can add users  and see the samba server  ie  smbclient -L bob
-Uroot%secret
I set the password for the Administrator account and it is also set uid 0.
I set the secrets.tdb password  smbpasswd -w secret.
I also have a ldap-secret file.
I checked the SID for net getlocalsid to the SID's in the ldap database, all
matched up.
I tried running net rpc join -Uadministrator%secret
For simplicity all the passwords I set are the same "secret".

Could someone please explain what the command;

  net rpc join 

is trying to authenticate?  Why can't it create a "workstations account"?
What "administrator privileges" is it looking for?

I am able to join the domain if I don't use the ldap backend.
What's the magic setting for ldap?

Thanks,

David Mongan