Just to clarify I have confirmed that the settings are not set to external speakers.
I have Samsung 37 LED TV (UE37C6000RKXXU) and all of a sudden no sound from any input device (Virgin TIVO, DVD, Wii or even play a movie clip via USB stick). It worked fine and is now JUST outside the warranty period. I have nothing on headphone output either.
Any suggestions ? Searching the internet this seems to be a common problem.