Your dvr should not be recording shows with unsynced video and audio. I have noticed that many of the late night tv shows have audio delays ranging from 1 to 2 seconds. Do you notice the delay on shows you record at other times?
Its mainly late night shows that have the delay.. But no recently my premium channels have audio problems too. Recently while watching movies on HBO or Cinemax channels the sound cuts out after 15 minutes and i have the change the channel and go back to get the sound to work again.