Comment 3 for bug 360494

I've observed this problem as well. On our install of Ubuntu Server 10.04, whenever the system resumes from being idle, we get locked out. The password for the active account no longer works, and the lockout screen does not allow us to switch users to shutdown. The only option at that point (if no one logged into the server via ssh before the lockout) is to do a hard reboot.

Our solution, which seems unwise but works, is to set the permission for /etc/shadow to 777. Or you could just configure gnome to not display the lockout screen on resume. Neither solution is optimal. Someone else suggested setting /etc/shadow permission to 640, but that does not work.