[Samba] Group mapping only working for initial group?

[Marco De Vitis]

Hello,
on my Samba 3.0.14a PDC (Debian Woody) I created a local unix group 
named "gpusers". Then I mapped it to a new NT domain group named 
"GPPower":

# net groupmap add rid=1005 ntgroup="GPPower" unixgroup=gpusers

Then added a user "mdv", who already had its own initial group "mdv", to 
the new gpusers group:

# usermod -g mdv -G gpusers mdv

So the situation for mdv is the following:

# groups mdv
mdv : mdv gpusers

I finally added the GPPower domain group to the local "Power Users" 
group on a domain client (Win2000Pro).
In this situation, when the user logs in on that client, he is NOT part 
of the Power Users group.

Instead, if I change his initial group:

# usermod -g gpusers -G mdv mdv

# groups mdv
mdv : gpusers mdv

...then the user correctly appears to be part of the local Power Users 
group on the domain client.

Shouldn't group mapping work also for groups other than the initial one?

Thanks.

-- 
Ciao,
  Marco.