Didn't see a hint for this one out there, so I thought I'd throw this out in case anyone else runs into this problem. I was having some kernel panic problems with my Ti Powerbook yesterday (apparently due to a bad USB peripheral) that caused my machine to lock up several times which resulted in a few hard resets of the laptop, which didn't appear to cause any harm.
This morning when I tried to start up iTunes I received an error stating that either the library was locked or I did not have write permission to it. I figured that this was most likely related to the problems I had yesterday, as I was burning a CD during one of the lockups.
After a bit of mucking around the system I was able to come up with this not-so-elegant workaround. I made my changes from the command line, but you should be able to do this from Finder as well.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030102060845695