Check posts 60 and 63 to see if they will help you. If they don't, then it could be a bad card. Does the problem follow the card? E.g., if you swap the new card you put in the sub (you didn't indicate where you put it) with the rear receiver or vice versa, does the same problem follow the new card (no sound from the device it is plugged into)? If it does, it's the card. If it doesn't, the problem lies elsewhere.
Let us know.