I've been enjoying my time on XP12 so far. It is running well, 30-45 fps, on a mid-tier PC.
Does it need work? You bet it does LOL, for me downtown Orlando is pretty much missing. I hope they address that issue in coming updates.
Sounds like the conflict started since you installed the ORBX sceneries. Have you tried uninstalling the ORBX sceneries to see if everything goes back to normal?
The Addon Scenery/scenery folder contains .bgl files that automatically load when FSX starts. They do not appear in program Scenery management screen, nor should they....you do not have to add them inside FSX. Hope that helps.