WARNING!: Upgrading to Quicktime 7.7 breaks "Purchased" tab in iTunes 10.4 Store
iTunes 10.4 comes with Apple Application Support 1.5.2. As long as you have that version of Apple Application Support, the purchased tab in the iTunes Store will work.
Both Safari 5.1 and Quicktime 7.7 come with a newer version of Apple Application Support, 2.0.1. If you install either update (or both), then the purchased tab in the iTunes store will be blank.
The Quicktime 7.7 is especially annoying since that's a security update. So basically you can either have access to purchased items in iTunes 10.4, but run an insecure version of QuickTime or have a secure version of Quicktime, but lose access to purchased items in the iTunes store on your PC.
Come on Apple, can't you at test your software on Windows before updating it? This plus the annoying sync crash when optimizing videos (photos) shows Apple doesn't test anything. iTunes 10.4 for Windows really *****.
iPad 2, Other OS, iOS 4.3.5