I have a V6 box which randomly loses sound..this usually happens when you change from one channel to something else, be it another channel, a recording or catch up, you get the idea.
To get the sound to come back on you have to just keep channel hopping until the sound comes back on.
Has anyone else got this issue
Have you tried, using you remote
pressing Home > Help & Settings >Settings > Audio > Dolby Digital > Dolby Digital to PCM?