Problem solved! There was nothing wrong with the Beomaster to start with. It was a Beolink 1000 I had in the same room. The Beolink kept sending the mute signal. I took the Beolink apart, cleaned it and put everything back together again and now everything is working fine again. What a relief!
Beoworld's twenty-eighth ninth prize winner and fifty-first second prize winner. Best £30 I've ever spent!