MotionMan
Lifer
Yup.
Did you ever move the library to another computer over a network? iTunes annoyingly keeps track of those movements and updates it's self. Possibly what happened there.
The only way that I know of to fix it is by reimporting the files 🙁
I did not move it. I cloned it to a new drive, then replaced the old drive with the new one.
MotionMan