Is it just me or was the sound out of sync of the 2nd half of Downfall last night? I also noticed it on the first half of Father Ted on Sunday night. About 2 or 3 frames I would guess.
It may not work for you but I've found with my two digi-boxes that switching channels back and forth can sometimes fix temporary problems. I guess it's something to do with them not buffering correctly. That said though, one of them was cheap and one old so it may just be those specific boxes.