[Samba] Samba 2.2.8 doesn't allow to write to group share

[Eric Geater 11/26/03]

Two issues, and I'll discuss them both:

I created on my NT4 domain a group called "branch99".  They're a "local
group" as far as NT is concerned, and it has two members; myself, and
another fellow down the hall.  My end quest is to create a share on a
Mandrake 9.2 box running Samba 2.2.8, and have it permit or deny file
access based on NT's typical discretions.

Using a recipe found in "Linux for Windows Administrators", I set up the
following smb.conf file:

[global]
   name resolve order = wins lmhosts bcast
   wins server = 172.16.128.1
   wins support = no
   domain master = no
   local master = no
   os level = 10
   preferred master = no
   workgroup = MARTIN
   server string = ZEKEJAX Test
   netbios name = ZEKEJAX
   security = domain
   password server = *
   encrypt passwords = yes
   smb passwd file = /etc/samba/smbpasswd

The group in question is this:

[branch99test]
   comment = Branch 99's Test Share
   path = /home/branch99
   valid users = @branch99
   browseable = yes
   read only = no
   create mode = 0660
   directory mode = 0770

I have already successfully joined the domain.

There is another (liberal rules) share that I can get to with no
problems at all.  I can even double-click the "branch99test" share, and
see the file that appears (a single text file created from the Mandrake
box; even my Windows box can open it).  But I can't write (create) in
the directory.  Can anyone postulate as to why?  I don't mind if
kstovall (not a member of "branch99") can't do it, but I'm in that
group, and I can't do it from an XP or 98 box joined to the domain.

Thanks!

Eric