Please disregard if not correct, but, do you have , eh, whats it called, a "galvanic separation" or whatever on your tv antenna or cable tv cable going to your tv ?
From your description when you turned it on again, it sounds as though a pulse, a sharp transient noise went through your amp and silenced it for a few seconds.
I once put my hands behind my power amp ( not a Bryston then) and I accidentally touched the rca from the preamp, the power amp made a noise in the speakers and shut itself down. Had to turn it off and on again. I think the rca was a bit loose in the jacket so the amp lost ground in one channel briefly. Scared me....., didnt use that cable again even though I tightened the jacket to fit very snug.