[Samba] trouble with file group owners with Samba 3.0.22.

[Ken]

We're running Samba 3.0.22 on a Debian system with kernel 2.6.16.16.
The file system is jfs with POSIX ACL and Security labels support.   We
have setup winbind so our Samba server grabs the user names and
passwords from our NT PDC.   I have tried creating files with two users.
  One is called scanner2 and belongs to the windows group scanning.
The other user is Administrator and belongs to the group Domain Admins.
  When I create the file with the user scanner2, the file's group owner
is scanning, which we want.   However, when I create a file with the
user Administrator, the file's group owner is Domain Users.  We would
like it so anything created by Administrator has a group owner of Domain
Admins.   Any help would be greatly appreciated.  Thanks.

--Ken