Apple has released iTunes 9.1.1. You can obtain it via the Software Updates component of Mac OS X’s Systems Preferences app.
According to Apple, the 102.1MB download addresses several stability issues with VoiceOver, addresses a usability issue with VoiceOver and Genius Mixes, addresses issues with converting songs to 128 kbps AAC while syncing and addresses other issues that improve stability and performance. iTunes 9.1.1 requires Mac OS X 10.4.11 or later.