This was possible in Breezy because gnome-screensaver didn't exist. As a possible workaround, you could use the existing xscreensaver project (still supported in Dapper).
** Changed in: gnome-screensaver (Ubuntu) Severity: Normal => Wishlist -- Missing seperate timer for locking screen https://launchpad.net/bugs/39968 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs