Comment 8 for bug 477832

So you've found the info better than I did! I reckon you did not issue this command through VNC? In that case, that would make things trickier. As I suspected, there's something wrong with ConsoleKit, which should at least have considered you as local for my tricks to work. You may get more information by running the ConsoleKit daemon manually, just like you did for PolicyKit: it's /usr/sbin/console-kit-daemon.

I'm not sure you should open a separate report right now, because what we are debugging is not a problem in users-admin, as it's getting broader with every step we make. It may well be that the whole failure is linked in some way that I can't really explain now, as I'm not familiar with ConsoleKit. For now, I'm moving the bug to that package, and another against update-manager, hoping that somebody can help debugging the links between both problems.