This is probably a long shot, since we have different tvs. I have a 52in RCA projection television. The fix seems so simple that I didn't think it would work. All I had to do was unplug the tv from the wall for 30 minutes to an hour. It has worked great since I did it. I was told that cable companies send s closed caption signal into homes that causes this problem with the sound on RCA televisions. The funny thing is I was about to toss the tv until I came across the fix online. It's worth a try.

Your TV needs a SSB module replaced. It is a small circuit board that plugs in just like a computer memory card. You push it sideways and pull up lightly. It is a common problem for these to go out and loose audio. They will cost about $125-$150.