I know upgrades are supposed to work, but they almost never go 100% percent right.
Use dpkg/synaptic to backup your installed packages and backup your /home...then commit to the time to going fresh install. If you use LTS releases, you'll only be doing it at most every other year.
I've had very good luck lately simply adjusting my sources file and typing apt-get dist-upgrade lately - though this is using Mint as the base distro (which in turn uses Ubuntu too).
Use dpkg/synaptic to backup your installed packages and backup your /home...then commit to the time to going fresh install. If you use LTS releases, you'll only be doing it at most every other year.
IMHO, it is worth the time.