Preupgrade results in inability to start x

[Kevin Kofler]

Claude Jones wrote:
> Additional detail: The 'acorn' thingy appears during boot, and at the
> end of the process, the little rotating circle appears momentarily
> appears followed by the splash screen, then, after another moment, the
> splash screen goes away and a little computer icon appears in the middle
> of the screen with some text that says, "Oh no, something has gone
> wrong. A problem has occurred and the system can't recover. Contact your
> administrator"....

This looks like it's trying to start GNOME, not KDE Plasma. It's the error 
GNOME 3 outputs when something is wrong.

        Kevin Kofler