OK, I have now found out something... not sure it's a solution though...... I started my system and put on my headset - and the whining was there. Still wearing the headset I unplugged it from the mixer, and plugged it directly into the mbox - and DEAD quite!
And also when I am plugged into the mixer and I mute the realtek channelstrip the whining becomes a little bit more evident than with that channel open. Also a slightly different change in the volume of the whining when muting the channel strip for the mbox - or both of them - so a thought occured... stupid me didn't realize it before, but plugged into the mbox itself it's quite and nice, and when I plug into the mixer, it is whining as heck. even with the channels muted - all channels - so I am now convinced it is a grounding problem... I think I'll just lay out a grounded distribution strip from my kitchen and try if there is any trouble, and maybe try individual devices in the grounded strip
ill report back when I've tried.