I've stumbled more or less in the same issue. I also got the progress bar slowly moving then I understood that something was wrong.
I was able to ssh to my hybrid and then perform an apt-get upgrade, just to see that only a subset of packages where going to be upgraded while the rest being kept back.
Nevertheless this made me get through and made possible to have my hybrid back and running.
To what I've seen there is a bug in the apt-get indexes (also in this post Bandito is saying the same thing -> http://plutohome.com/support/phpbb2/viewtopic.php?t=1146
) and I think that's basically why automatic upgrade failed and is forcing me to do it by hand and piece by piece ...
Currently I'm playing with apt-get trying to to get all packages updated, and if you are not willing to go for a fresh install I think you have no chances left.