Thanks for the feedback. I was just reading through my older posts when I first got the M500 it was always turning itself on! Anyway, have ordered a new power adapter (3rd) party and perhaps this will do the trick. The impact of weather and brownouts in my area affects everything plugged into the wall. This is part of a system plugged into a UPS and conditioner. When it drops to standby, the wifi stays on, as do the rest of the components, so I don't think it's weather in this case.
MAC OSX 10.8.2/Belkin 5Mhz wifi/SB 500/B&O 9500/YSAudio 3 Tube Amplifier/B&O RL 60.2 (6)