I had this same issue and same solution. I believe it was caused by using etckeeper to restore files in /etc (including /etc/passwd and /etc/shadow).
-- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-screensaver in Ubuntu. https://bugs.launchpad.net/bugs/45368 Title: Unable to unlock screen (Dapper) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-screensaver/+bug/45368/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
