(In reply to comment #5)
> Looks like the X server may not shut down cleanly. Is there something
> interesting in its stderr output? You may find it in the display manager log
> file(s).

I redirected the output of startx to a log file, but
there's nothing interesting in there AFAICS.

> (In reply to comment #4)
> > > Can you still log in via ssh at that point?
> > 
> > Yes.
> 
> What happens if you try starting X again or switching VTs using chvt from
> ssh?

Sorry, I just assumed that ssh would work because the machine
still responds to SysRq input. I cannot test this ATM.