That workaround only works when starting software-properties from the control center, but the package sources dialog can't be accessed from synaptic like that. Better symlink /usr/bin/software-properties to /usr/bin/software-properties-gtk.
-- software sources icon in control panel does nothing https://launchpad.net/bugs/84290 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
