adding group membership to ldap users
 

I have a Debian lenny ldap server that holds username and pasword information. When users log into ldap client workstations(lenny) i want to add the users to groups on the workstation. I have added this line to /etc/security/group.conf on the workstation:
*; *; *; Al0000-2400; audio,cdrom,floppy,fuse,plugdev,video,scanner
To /etc/pam.d/gdm I have added the following line:
auth optional pam_group.so

Any suggestions why this doesn't work for me?