Let's pretend this fixes the issue.

The problem seems to be with the data file that iTunes create, so I let iTunes create a new one, and it worked for fine me:

* Open iTunes, and go to File->Export Library
* Save the library somewhere in your hardrive
* Complete close your iTunes
* Go to your music folder, open the iTunes folder and move to another location both files: the Itunes Library data file and the iTunes Music Library.xml DO NOT REMOVE THE FOLDERS
* Open iTunes again, and it should show up that your library is empty, now, go to File->Import and load the file you exported in the second step.

The Library import will take a while, but after it finishes you will have a new iTunes library with all your stuff in it.

If something goes wrong, just copy the original data and xml library files to the Music->iTunes folder.

Seems to kill your date added, played, etc metadata, though. THANKS, APPLE TESTERS!!! This really is sorry quality assurance/control for iTunes. And to think I thought the last set of "errors" in an iTunes update was done purposefully. Ha. Conspiracy theorists abound.

Could take a while.