Have you checked the mute isnt active or box or TV? After that try a different scart lead as Noel said.
Not nice highjacking someone's post. Look in the usual threads for codes http://forums.afterdawn.com/thread_view.cfm/650377
And mute buttons are not engaged? Take the cable feed out of the SV and plug it directly into the TV, do you get sound now on the FTA channels?