cannot login after Xserver dies, not even after reboot (F18 Alpha)

[John Reiser]

https://bugzilla.redhat.com/show_bug.cgi?id=858741

If /usr/bin/Xorg dies, then all subsequent attempts to login fail,
I get the blue-streak-and-stars background image, then "Oh no!
Something has gone wrong. ..."  Clicking the LogOut button
just repeats the failure.  This behavior persists even after reboot.

How do I clean up so that graphical login can succeed?

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