"Add" is available in the Services tab (for the services that support it), even if there's no Bluetooth devices. It should probably be disabled if there's no adapters.
Filed upstream: http://bugzilla.gnome.org/show_bug.cgi?id=525578
ndisc6-0.9.9-1.el5 has been submitted as an update for Fedora EPEL 5. http://admin.fedoraproject.org/updates/ndisc6-0.9.9-1.el5