Maybe the one you were working with is not the original FSX AFCAD?
I can only confirm my AFCAD is the default, it's named APX08100.bgl and it's labeled as "stock" when opened with any AFCAD editor, and it has exactly the same parkings listed in GSX.
I have no idea why mine would be any different...I am stumped
As I've said in my previous message:
Check if you have another AFCAD in conflict: go to a parking that works, and select the "Customize this parking position" option from the GSX menu. Even if you don't really customize anything, it will say which AFCAD GSX is taking informations from.