Thanks for all the advice. My current plan is to see if it reoccurs after the power cycle. If it does I'll them try the above suggestions as the ADA is hard to get to as it is shelf mounted a couple of meters above the floor and awkward to get to. The ADA has been in use for about 18months and continually powered (minus any power offs of the circuit when electrical work has been done).

HT:M80,VP150,QS8,EP500 Outside:4xM3 Office:AudioBytes, Rumpus: M60,VP150,M22 Portable:2 x Airs