In reply to jussy:
It may have been sorted out by now but last year there was a licensing problem with AC-3 audio in several apps. AC-3 is an audio standard owned by Dolby and they were asserting their rights and asked Apple to remove any app that wasn't paying them a royalty.
What this meant was that you had to rip the DVDs making sure you used AAC (another audio coding standard) rather than AC-3. You also had to make sure that you didn't update the apps as the updates didn't have AC-3 decoding so you'd get films showing but no sound.