This is particularly a problem for users upgrading from previous versions of Ubuntu, as several menu items (e.g., network) have "gksu" in the command line, and the menu entries are not properly reverted during upgrade. It took me a while to figure out that I had to revert (or manually remove the "gksu") from many "administration" menu items in order to actually do anything, since root is apparently locked out of policykit.
This is particularly a problem for users upgrading from previous versions of Ubuntu, as several menu items (e.g., network) have "gksu" in the command line, and the menu entries are not properly reverted during upgrade. It took me a while to figure out that I had to revert (or manually remove the "gksu") from many "administration" menu items in order to actually do anything, since root is apparently locked out of policykit.