I had the same issue and the problem was that menu.lst had root=/dev/hda2 instead of /dev/sda2. I reported this bug but I cannot find it anymore. I may have not completed the process.
-- Feisty: unbootable after dist-upgrade https://launchpad.net/bugs/77233 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
