HELP! No X on startup

[D. R. Evans]

We just had a long power outage. When the power returned, all my
machines came back fine except my Kubuntu main desktop machine. It is
rebooting, but X isn't starting and I'm being presented with a
non-graphical prompt.

This machine has been running dapper fine for about 18 months, and I
haven't changed anything to do with X for about 6 months (which is
when I loaded the then-current nvidia driver). It's always worked
fine, and I have no idea why it's suddenly decided to go
non-graphical.

I haven't the foggiest idea what to do. Can anyone please help?