gnome gdm diable_user_list

[n dhert]

FreeBSD8.0, gnome2-2.28.2_1, using gdm to login.
Gdm login screen presents a list of all users on the system to choose from.
I don't want the list, just a prompt for a username and password.
I tried
# gconf-editor
this graphical config program allows to set in apps / gdm / simple-greeter
the setting  'disable_user_list' to checked (default is not checked)
after setting it to checked, closing the program, rebooting
I still have the user list at the gdm login window.
I verified with starting the gconf-editor again: the option is still checked
..
(also $ gconftool-2 -R /apps/gdm/simple-greeter shows: disable_user_list =
true )

Why do I still have the user list?
How to fix?