samba - Feb 2008 - problems with GID while mounting shares

Can anyone say me why, even with this string, 

"smbmount  //pbt3/Condivisa /home/rob/Condivisa -o
username=rob,password=XXXXX,uid=rob,gid=ufficio"

I cannot login as UID = rob GID = ufficio ???

here's something else.

On server:

pbt:~# smbstatus 
Samba version 3.0.24
PID     Username      Group         Machine                        
-------------------------------------------------------------------
 8037   rob           rob           192.168.3.111 (192.168.3.111)
Service      pid     machine       Connected at
-------------------------------------------------------
Condivisa    8037   192.168.3.111  Thu Jan 31 13:55:54 2008
Tutto        8037   192.168.3.111  Thu Jan 31 13:13:57 2008
No locked files
pbt:~# 

pbt:~# groups rob
rob : rob ufficio musica
pbt:~# 


On client:
rob@tiranno:~$ groups
rob dialout cdrom floppy audio video plugdev ufficio musica
rob@tiranno:~$ 


Do you need other stuff to debug this?!?
thanx for every idea!

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