Hum... it rings a bell now.
As you (Mark) are loading and starting your flights from the CS727 pre-saved flight, it means that the, so to say, FSX's default generator system is switched on and hence, correctly set for how CS 727 should be. If you check the Cold-n-Dark.flt, under engine parameters, you'll notice that for every 3 engines, the GeneratorSwitch command is set to "true". As the 727's switches do not seem to be directly connected to FSX "default" electrical systems, FSX won't reckon the generators as "switched on". In other words, if I set my default Cessna with generator on, then when loading the 727 all will be fine. ;) See what I mean?

Now I can almost say I found the deal. ;D

Thanks a lot DrJ1 for lighting things up here and yet again, Mark, for your tireless and precious help! :)