You know...this is how I would handle it --
Exchange is FREE, short of shipping.
Get the correct board that matches your TV.
If the HDMI was bad on that board...you get a new board to test.
If it STILL FAILS (and it shouldn't) you're done.
If it does lose sound, the First thing on my mind would be if BOTH the DVD and CABLE box are routed into an audio amp, then OUT to the TV set.
TV's don't like that setup because the TV only wants to handshake with one unit, and when you have an cable/dvd box connected to an amp THEN to a TV set....you may get double-handshaking and it can affect the sound or the picture !
NEXT....if you don't have an AMP....and it still doesn't work...see how much time you have to RETURN that board.
Try selling it on EBAY before you have to send it back for a 20% restocking Fee.
Here's the problem that Tim or I would have....if we didn't order the board and attempted to return it at full price, they will look at our Order Requests, our PO numbers, and they will NOT MATCH.
They'll match your order, not ours.
Those are the things I would do in your situation. Exchange FIRST (and if they don't have one) EBAY second, and send it back to them as a WRONG PART.
They may let you slide if you push the wrong part issue.