Hmm...did you make that file? What are the backports uncommented for? My information may not be entirely accurate since I haven't used Ubuntu since just after Hoary was released. I had the universe and multiverse repositories, but never those backports.
First make a backup of the file (cp sources.list sources.list.bck). Maybe try commenting the two last lines, since they don't seem to be working anyway judging by your 'apt-get update' before. Then replace every instance of 'hoary' with 'breezy'. Now apt-get update. If that goes perfectly smoothly, you can perhaps try an apt-get dist-upgrade.
DISCLAIMER: I haven't used a Debian distro since Hoary was released. I'm not garanteeing this will work perfectly, but right now I don't see why it shouldn't.