Does this happen on other inputs?
Also, what happens if the game console is unplugged from the TV? Does the option allow you to get audio fro the TV?
Also, what model TV?
I have a Samsung HDTV used with XBox 360. Sound does not work unless headphones are plugged in (sound only comes from headphones). Plugging/unplugging headphones does nothing to correct problem. TV is updated to latest firmware. Settings/sound selection shows "TV" but it is grayed out--meaning you cannot change that selection. Have tried everything except calling for a repair. Please help!!