To roll back to iTunes 10.7 first download a copy of the installer from here, uninstall iTunes. Probably best to also remove other suppporting software, e.g. Apple Application Support, Apple Mobile Device Support & Bonjour. Reboot. Restore the pre-upgrade version of your library database as per the diagram below, then install iTunes 10.7.
See iTunes Folder Watch for a tool to scan the media folder and catch up with any changes made since the backup file was created.
I found your original post of this solution on a non-apple controlled forum.
Would you mind sharing where?
It fixed it that night, though I was up till 5 am before I got everything working. Jayzus, talk about teaching me a hard lesson before installing apple's idea of "upgrades".
Probably a good time to start thinking about a complete backup strategy for your library and other important data.