Upgrade ended Half-way between ubuntu 11.10 and 12.04, how to full upgrade?

When this happened to me because the update process had "too many errors" (whatever that means), I did the following.

1. Boot the recovery mode of whatever kernel still works.
2. Your / partition will have been mounted as read-only because you booted in recovery mode. Run fsck Check all file systems from the recovery menu. Hopefully it will complete successfully at which point your install partition will be remounted as read/write.
3. Enable networking so that you will have access to the Internet when you try to fix your packages.
4. Attempt to Repair broken packages

Maybe this will not be any more successful than your previous attempts to fix the packages. But I figured it might be worth a try. It seems to have worked for me.

You mention that your apt sources were updated during the partial upgrade. The first thing you should do is verify this by checking the /etc/apt/sources.list to make sure the deb and deb-src lines reference precise instead of oneiric. If they do not, edit the file to correct this using the following command:

sudo gedit /etc/apt/sources.list

Once the sources have been updated, one way to complete the upgrade would be to enter the following two commands through the terminal:

sudo apt-get update
sudo apt-get dist-upgrade

The error message you got from the update manager about needing a partial upgrade is that some of the updated packages want to pull in dependencies that are not currently installed, which is not particularly surprising when the new packages are from a new distribution version.

Once that completes, you should be on the new version. To clean up packages that are no longer required by packages that you explicitly installed, run the following command:

sudo apt-get autoremove

Check that the list of packages it offers to remove looks sane before continuing.

Solution was to reinstall from scratch. Nothing lost because ubuntu keeps your "home" folder