So I've been trying to move ahead here with introducing controls to the system, and I have somehow taken a step backwards...

Despite having worked fine before, the KEAD6 and KE-USB108 seem to be having an argument about who's controlling the brakes.
All I did was disconnect everything to do final wiring, and put everything back where it was, except for bussing the common leads in a different location (to minimize "home runs" to the terminal strip).
I didn't change anything at all on the KEAD6, wiring-wise.

I have left and right brakes properly assigned to joystick buttons on the 108, and they work fine. However, the KEAD6, despite being set up properly (directional axes, correct keyboard assignments [thru FSUIPC], etc) no longer send prop, throttle, and mixture commands. all it does- and this is weird- all it does now is send one of the brake commands (not sure which one) when throttle #1 is brought back to idle. 

I've triple-checked all settings and assignments in FSUIPC and FS9, re-created the profile for the KEAD6, rebooted the sim, and it still does the same thing. I'm willing to believe this is my system's way of telling me "I can't handle even these few things on my USB even though I did so previously; sorry", but there may be another explanation...?

Another note on USB function with this setup: I noticed even before I started today that despite not having unplugged anything, Windows insisted on re-discovering everything on the USB. This is also puzzling... 

Bizarr-o... I just re-plugged everything into the USB hub so they start on the port on the left (had that open previously)... now throttles, etc. work as they should. As for the New Hardware Wizard, I haven't updated in a while and I've tried to turn the damn thing off to no avail.