unable to lock down Gconf mandatory settings gnome screensaver timeout Redhat 6.4

We are trying to force 5 minute screensavers for users. We do not want them to be able to change these settings. Running the settings below, greys out everything but the timeout variable and users can still change the timeout value.  We are running Redhat 6.4.  Any ideas why this particular value won't stick?  The gconf.xml.madatory is listed below also.

/usr/bin/gconftool-2 \
             --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
             --type bool \
             --set /apps/gnome-screensaver/idle_activation_enabled true
/usr/bin/gconftool-2 \
             --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
             --type bool \
             --set /apps/gnome-screensaver/lock_enabled true
/usr/bin/gconftool-2 \
             --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
             --type string \
             --set /apps/gnome-screensaver/mode blank-only
/usr/bin/gconftool-2 \
             --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
             --type int \
             --set /apps/gnome-screensaver/idle_delay 5

more %gconf-tree.xml