Kevin,
the strong suggestion is that there must be something in the \Addon Scenery folder, or sub-folders, that is causing problems. Is it possible to show us -
a - what is in the \Addon Scenery folder?
b - what is in the \Addon Scenery\scenery folder?
c - what is in the \Addon scenery\texture folder?
It is a long time since I did an FSX install but I suspect that, after this initial install, there should be nothing in \Addon Scenery other than \scenery and \texture folders and these should be empty. I am wondering if, during your early attempts at compiling direct to these folders from ADE, some file(s) has got stuck in here somewhere.
Personally, when I compile from ADE, I allow all compile BGL's to go into \FSX\Bgl folder in the ADE installed folders. I then copy the files into appropriate positions within my \Addon Scenery in FSX. You should do whatever is most comfortable and convenient for you.