Comment 2 for bug 477832

Thanks for this detailed report. To make it completely clear, you experienced these problems after upgrade and before running users-admin, so that it cannot be the culprit? I'm asking that because it may also have led to that situation, it's a problem we've already seen.

About the admin rights issue, being member of the admin group should be enough. What does /etc/polkit-1/localauthority.conf.d/51-ubuntu-admin.conf contains? Can you list the groups you are member of? You can also compare those memberships with those of the user that still works (relatively easy reading /etc/group). Are you able to perform upgrades using update-manager from the buggy user account?

About the general issue, I'm not sure what can have caused that, except update-manager itself. Once we have sorted out the problem specific to the gnome-system-tools (they may well be a mere consequence of the global bug), I think I'll move the bug to the package update-manager.