Comment 23 for bug 78470

In addition to the previous, it looks like a problem with X and Fast User Switching since the screen will go black but the system still responds to keystrokes. Pressing Ctrl+Alt+Backspace will end the session, and GDM sound effects can be heard. Quickly pressing the Power button on the PC will cleanly shutdown the PC showing text mode. Occasionally, it has been possible to get back to a login screen by pressing Ctrl+Alt+Backspace repeatedly.