The past three weeks, I noticed that whenever I tried to edit MP3 / AAC ID3 properties in iTunes (4.0.1), it would commit the changes to the file(s), and then immediately crash. iTunes is perhaps the best way to manage, name and ID3 tag files, and I love its global editing features. Crashing sucks. Even not saving changes to a file caused crashes to occur. So how did I fix the problem?
You guessed it, repair permissions. Just go into your /Applications -> Utilities folder, run the Disk Utility app, and select Repair Permissions. I noticed the permissions were set wrong on an item in the iTunes.app package having to do with id3 usage. Voila, problem solved.
[robg adds: This small hint has inspired me to finally finish writing my own "OS X Troubleshooting 101" hint (it's been 'almost done' for um, quite some time now...), which I'll try to get posted before the week is out ... and repairing permissions is definitely part of that process, as noted here for a number of other OS X issues.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030920163247796