I've got a theory about this one, RAF. For a long while my SMS-1 left its light off even through power outages, but I recently turned it back on and since then it's been coming on any time there's a brief power outage. When I originally turned the light off, I'm 99% sure I was in the menu - and when I exited I saved my changes. My theory is that turning the light off while in the menu and then saving the settings causes it to remember the light mode as "off" even if the unit is turned off or loses power - until the light gets turned on again, at which point it appears to abandon that "light off" memory. I haven't tried turning the light off again while in the setup menu to see if it remembers - I'll have to try it soon.