You may hear no audio when playing videos purchased from the iTunes Store.
This only affects content purchased from the iTunes Store. You may be able to play this content in QuickTime Player. The content will sync and play normally with audio to iPod and iPhone.
Update to QuickTime 7.4.1 to restore full playback of the affected content in iTunes.
Important: Information about products not manufactured by Apple is provided for information purposes only, and does not constitute Apple's recommendation or endorsement. Please contact the vendor for additional information.