This could be policy-kit related. Can't find any error messages about the problem in /var/log
** Also affects: policykit (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gnome-session in Ubuntu. https://bugs.launchpad.net/bugs/975157 Title: Can't reboot/shutdown with two user logged in Status in “gnome-session” package in Ubuntu: New Status in “lightdm” package in Ubuntu: New Status in “policykit” package in Ubuntu: New Bug description: On Ubuntu Precise, with two users logged in (fast user switch etc..), the computer no longer responds to reboot or shutdown. Both trying it from the Unity session and from lightdm fails. ProblemType: Bug DistroRelease: Ubuntu 12.04 Package: lightdm 1.2.0-0ubuntu1 ProcVersionSignature: Ubuntu 3.2.0-21.34-generic 3.2.13 Uname: Linux 3.2.0-21-generic x86_64 ApportVersion: 2.0-0ubuntu4 Architecture: amd64 Date: Fri Apr 6 15:47:59 2012 SourcePackage: lightdm UpgradeStatus: Upgraded to precise on 2012-02-07 (59 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-session/+bug/975157/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp