How to fix broken init

[Lee Willis]

I left one of my machines running a dist-upgrade to bring it up to date 
with edgy-latest around 10 days ago. Unfortunately something seems to 
have happened during the upgrade as when I returned to the PC the power 
was off. I guess either a power failure (Although nothing else in the 
house went off), the machine decided to suspend/hibernate itself, or my 
2-year old had fun with the bright green button :)

Whenever I try and boot the machine into any of the installed kernels 
the boot process just hangs. Even trying to boot into single user 
doesn't actually get me to a shell. The kernel seems to load OK, and I 
get lots of output about stuff being set up, but it never seems to get 
anywhere that I can do anything. I'm *guessing* that the old init 
process had been removed, and the new upstart process hadn't been 
installed before the power went [It was one of the changes to be made by 
the upgrade IIRC].  I suspect that if I could get it booted then I'd be 
able to get it sorted with some dist-upgrade or dpkg-configure magic - 
however how can I get to that point?  I have a live CD if that'll help 
[Perhaps boot off the live CD and run dpkg-configure with --root set to 
the hard drive?]

Any ideas?

Lee