My 42" HGTV has lost sound. The picture is fine? I haven't changed any settings or anything. Any thoughts on what could be happening.

I think you mean HDTV (Not home and garden TV ;) Lol )

Anyway... I assume you have a cable/sat box? Can you check it on another TV? If you have cable... try plugging the cable directly into the TV... try something else in the TV (video camera? video game?) something that makes sound so you can test it