Happened last night- it totally lost sound. Picture's perfect, though. I tried shutting it down, starting over. Finally I shut it off for the night hoping it was a fluke. Started it up this this morning- same thing! It's a 4yr. old Panasonic 40" LCD high def. I bought it at Circuit City, now out of business. It was a demo & I didn't purchase a warranty. What should I do? Any help is appreciated. Thanks..