[Samba] setting access rights for shares not working for groups

[Gotrar Yahoo]

Hello everybody,
    my english is very poor sory for your comprehension

lan :
 OS : debian testing
DD : SCSI
 PDC : Samba 3.0.14a

user : PC WIn2000 SP4

I have a big problem of slowness on the divisions of Samba... 5 to 10 
seconds to post a repertoire and copies it from the various divisions is 
very slow.... I do not know or that comes : - ( 
in my smb.conf:  socket options = TCP_NODELAY SO_RCVBUF=4096 SO_SNDBUF=4096
thank you of your answer

Gotrar