If you've got 10.3.9 or earlier, and downloaded iTunes 6.02 and hit a problem with running Permissions Repair using Disk Utility (and many people have...) then the fix that seems to work ..God knows why... is, to quote from the relevant Apple Support Forum...
"Go to HD>Library>Receipts and trash all iTunes .pkg files EXCEPT for iTunesX.pkg and iTunesPhoneDriver.pkg"
It's been a total fix for me. Er... why? Greater minds than mine will doubtless know the answer to that question.