I'm using the latest version of AFCAD and running FS9 on Windows 98. I designed a new airport in the Sahara near Libya, and when I tested the area there was a mountain in the way! ::)
Now after I've flattened the extra bit of mountain away ddhelp.exe performs an illegal operation when the flight planner is opened. This is extremely irritatating as I need to restart. Is there anything I can do to fix this problem with AFCAD or the Flatten switch while still preserving my airport?