How to diagnose loss of X/GUI after latest kernel upgrade in 8.10?

[Chris G]

I just did the latest kernel upgrade on my xubuntu 8.10 system (to
kernel (to 2.6.27-14) and now the X GUI doesn't start up.

I still have virtual consoles working (fortunately, I'm mailing from
one) so most of the system is working, all that's missing is the GUI.

On reboot I get the xubuntu splash screen with the moving bar but
that's my lot, when it disappears I get no login screen or anything
more at all.

There don't seem to be any errors in /var/Xoef.0.log.

Does anyone have any idea what the problem might be?  How can I set
about diagnosing the problem?

-- 
Chris Green