Some users are experiencing an issue with iTunes 10, generally after restoring from a Time Machine backup or upgrading to Mac OS X 10.6, where their music library is not viewable in the iTunes window. Though the music is not viewable, the files are still located on their drive.
The problem is an odd one. When users import music from a CD, the tracks will play, though the track listings do not appear in the library window. Existing tracks are also not present. The same holds true for Movies and TV Shows. A growing forum on the Apple Support Discussions reports the issues:
"New machine, moved all my data over, updated all the software, tried re-installing OS from disk and then doing Software Update, tried reinstalling iTunes 10, nothing works. I can't see any of my music even though it's all there." -mrfett
One user has posted a screencast of the issue.
Many users who experienced the issue prior to the release of Mac OS X 10.6.4 reported it fixed with the update, though others say it exists in 10.6.4. Try reinstalling the Mac OS X 10.6.4 update using the Combo Update Package from Apple. You should also be sure you have the Snow Leopard Graphics Update installed.
You may consider reinstalling Mac OS X 10.6.4 from a disc with a clean install. Of course, be sure to have all your data in a secure backup like Time Machine. When restoring from the Time Machine backup, do not restore iTunes, but instead download a fresh version from apple.com.
Once iTunes is installed, restore the contents of your music library and drag the files into the iTunes window (which should make a copy into your new iTunes Library file).
Have you had issues with iTunes 10? Let us know in the comments!