Peter :No idea! 
Try resetting the options!
Done, but nothing changed 
I've unplugged for several minutes all the system from mains and from ML.... then re-plugged, but no changes.
I've reset the 3 system options: main room VideoOpt=2 and AudioOpt=0, link room LinkOpt=6... again no changes. 
Trouble: the wake-up caused by a very very slight contact with the beo5 sensitive wheel on the bed 