[Samba] Valid Users in Samba 3

[Lahners, Jeremy]

All -
  I'm having a problem with the "valid users" directive working.  I have an Accounting share that only the Accounting department should have access to.  However, I am unable to lock the directory down so only they can access it.  I am running samba-3.0.0-2 from an RPM on RedHat 9.0.  Below are details of my trials.  This is a pretty urgent need, please.  Thank you!  
 
smb.conf
[global]
        workgroup = SCHEMMER
        server string = Project File Server
        security = DOMAIN
        password server = quicksilver.schemmer.com, fs2omaha.schemmer.com
        log level = 10
        log file = /var/log/samba/log.%m
        socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192 SO_KEEPALIVE
        preferred master = No
        dns proxy = No
        wins server = 192.168.100.210
        ldap ssl = no
        idmap uid = 10000-20000
        idmap gid = 10000-20000
        template shell = /bin/bash
        winbind use default domain = Yes
        oplocks = No
        level2 oplocks = No
 
[Accounting]
        comment = Accounting Files
        path = /shares/acct
        valid users = "@Domain Admins", @Acct
        read only = No
        create mask = 0777
        directory mask = 0777

Output of "wbinfo -r smicheels"
10047
10024
10009
10040

Output of "getent group"
Acct:x:10047:platham,smicheels,gstoddard,cplum