Comment 5 for bug 1064584

This is a key bit:

Jan 17 07:54:33 workstation gnome-session[2959]: WARNING: Application 'gnome-shell.desktop' killed by signal 11

The lock screen is integrated into the compositor (gnome-shell) in 3.6. An unfortunate side effect of this is that if the compositor crashes, it will get auto-restarted, and we "fail open". In prior versions of GNOME, "gnome-screensaver" was an indepenent process.

Clearly it would make sense to attempt to preserve the "screen is locked" state, but that'd still allow a window in which the session was accessible. The real fix here is to figure out why gnome-shell is crashing and ensure it doesn't.