While you should have been able to make that upgrade, I would have downloaded the next iso and made a fresh install.
Do you have any data that's not backed up? If all your data is backed up, you might find it a lot less bothersome to simply re-install from an install disk. (the 14.04 disk) Or you can use a live CD to backup your data to an external drive and then install.
If the system has 'broken', and it sounds like it has, then trying to fix it will take three times as long as simply re-installing.