The same happened to me just now.
Have you found a solution for this problem yet?
I turned on my Samsung HL-S5687W this evening and I have no sound. Interesting since there was sound last night. I tried changing my TV input to see if that was the problem. I checked to see if the TV was on mute and I even went to check all my connections, and NOTHING. The only way my sound is working is through my DVD-stereo system. I even tried going to the TV menu to see if some of my options had changed. I need help on trying to solve this problem if the problem can be solved. I am going to try to disconnect and reconnect my cables. HELP.