Fedora :: System Shutdown Only Logs Out

I currently run kernel 2.6.34.7-66.fc13.i686 (sort of). When I select from the Gnome menu System -> Shutdown and select Shutdown from the dialog, my system only logs out, presenting me with the greeting screen. While this is a minor problem and I rarely shutdown my machine, it is mildly disconcerting.I have dropped back to 2.6.34.7-63.fc13.i686 and that shutdowns properly using this method. (Also, 2.6.34.7-61.fc13.i686 works properly). I can imagine that it might close some security issue in which an unauthorized user is able to halt the entire machine. Especially if this is something that will continue in future releases of the kernel.