[Samba] Samba Invalid user not working

[updatemyself .]

Hi All,

In my Samba File server i am not able to set an "invalid users"... option..
even if i set that, its showing in "testparm" result but there is no change
while accessing it...

My Samba Server is connected with Windows 2003 ADS and all the Domain Users
can
access the share with out entering, any other password ( samba password )
some modification
in /etc/pam.d/login, /etc/pam.d/gdm and /etc/pam.d/system-auth

OS        :- Red Hat Enterprise Linux ES (2.6.9-22.ELsmp)
samba   :- samba-3.0.21b-3  compiled using samba-3.0.21b-3.src.rpm

the users "rush" and "render" always having connection more then 200
because of this my samba share getting slow.. and its effected the
production

following is my smb.conf

#=========================== Global Settings ===========================
[global]

   workgroup = MYDOMAIN
   server string = Samba Server
   log file = /var/log/samba/%m.log
   max log size = 50
   security = ads
   encrypt passwords = yes
   socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
   dns proxy = no
#========================= Share Definitions ============================
   password server = 172.16.20.200
   realm = MYDOMAIN.COM <http://mydomain.com/>
   idmap uid = 16777216-33554431
   idmap gid = 16777216-33554431
   template shell = /bin/bash
   template homedir = /home/%D/%U
   allow trusted domains = no
   idmap backend = idmap_rid:MYDOMAIN=16777216-33554431
   winbind use default domain = yes


[volume]
        path = /vol08_1000
        invalid users = rush, render
        valid users = @Domain Users
        read only = No
        create mask = 0644
        security mask = 0755
        directory mask = 0775
        inherit permissions = Yes
        inherit acls = Yes
        inherit owner = Yes
        vfs objects = recycle
        recycle:versions = yes
        recycle:touch = yes
        recycle:keeptree = yes
        recycle:exclude = *.tmp,*.temp
        recycle:repository = /home/.Trash/%U-%m-%d