I did three upgrades and a couple of fresh installations without a hitch.
This appears to be the norm. However, a few people have had your experience,
unfortunately. Does it list recovery as one of the options? Try that.

If not, then I would download the Live CD and burn it. Then boot into it and
back up your data. Then I would do a fresh installation.

If this is not to your liking, you could try to rewrite grub, also from the
Live CD and see if the problem is superficial or runs deeper. If it is
deeper then you can try to watch the boot process by getting out of
graphical mode and watch to see where it fails. Any Live CD could be used to
re-write grub.

I am not sure which grub you have installed. It sounds like grub2, but an
upgrade should keep legacy grub and not try to translate it. If it did try
that then that may be the source of your problem.

I'm having exactly the same issue.
I upgraded my box (Athlon, 378MB RAM, 40GB IDE HD on ext3 - I've been upgrading
every six months since version 5.04).
As it was installing the upgrade the error messages started (did not take note
and can´t access anymore)
After rebooting, same symptoms as you mention.
Even worse: when starting with the LiveCD, the HD can be seen, but not mounted.
I diagnosed the HD with LiveCD and it did not find anything wrong
I left it there for further analysis - did not have time to do much more yet.

Maybe it is not a HD crash, as I suspected... that would be good news.

Yes. I've been using Kubuntu since version 6.04 until know and have had only 2
or 3 successful upgrades. The rest, including the 9.10 upgrade, ended in
failure. Luckily, this time I had burnt a DVD of 9.10 and verified the MD5 key
(the first download was bad) before attempting the upgrade. When it failed, I
just proceeded to do a fresh install.

I think the best solution is to mount your /Home drive in a separate partition
thus allowing you to re-install your system as often as you want without the
need to backup your data. Besides, this lets you clean out all the bad
experimenting you may have (I did ;) ) on the O.S.

Recently, I have read issues where people did the upgrade and had problems.
They backed up and did a fresh installation and it worked fine. I am not
sure if this will be to everyone's liking, but it is worth a try. Not all
upgrades work for various reasons. Even some Windows 7 upgrades go awry.

Troubleshooting and fixing problems takes patience and time. Sometimes a
quick and dirty fresh installation is the best way.