iTunes 9.0.1 provides a number of important bug fixes, including:

• Resolves issues browsing the iTunes Store.
• Addresses a performance issue where iTunes may become unresponsive.
• Fixes a problem where iTunes may unexpectedly quit.
• Fixes a problem syncing Podcasts in playlists to iPod or iPhone.
• Fixes a problem sorting albums with multiple discs.
• Improves application syncing for iPod touch and iPhone.
• Genius is now automatically updated to show Genius Mixes.

You can upgrade by starting iTunes on your PC/MAC and selecting the 'Check for updates' from the 'Help' tool bar.