Comment 3 for bug 516684

I ran into this as well. I think it actually is a legitimate issue because if you run into a problem with the lucid kernel, it is entirely sensible that you'd want to boot an earlier kernel version and have it work. I ran into this in a Hardy -> Lucid upgrade.

You can workaround it by issuing the following commands at the tty emergency console;

mount -n -o remount,rw /
mkdir /var/run/network
/etc/init.d/networking restart
mkdir /dev/pts
mount /dev/pts
/etc/init.d/ssh restart
mkdir /dev/shm
mount /dev/shm

You should be able to ssh into the server like usual and start up any other services that may not be running.