Comment 12 for bug 557930

So, two things of note here in the logs.

First, from /var/log/daemon.log:
Apr 10 09:56:30 ubuntu kdm[3311]: X server startup timeout, terminating
Apr 10 09:56:31 ubuntu kdm[3311]: X server died during startup
Apr 10 09:56:31 ubuntu kdm[3311]: Failed to start X server. Starting failsafe X server.
Apr 10 09:56:34 ubuntu init: plymouth-stop pre-start process (4486) terminated with status 1

plymouth-stop is supposed to run before kdm starts; so the fact that it's running three seconds after kdm, and furthermore that it's failing, indicates a bug in the ordering.

Second, from /var/log/kdm.log:

/etc/gdm/failsafeXinit: riga 184: zenity: comando non trovato
/etc/gdm/failsafeXinit: riga 47: zenity: comando non trovato

waiting for X server to shut down ddxSigGiveUp: Closing log

It appears that failsafe-X, despite being shipped in x11-common, relies on both zenity and gdm - so isn't going to work on Kubuntu, where we have neither by default.