I've just downloaded and installed some scenery of Johannesburg and Cape Town, but both are causing CTDs, does anyone know of any fix? I can't find any, and can't see why the scenery isn't working :-(

I don't have that scenery but bad AfCad files are a common cause of CTD's. Try temporarily removing any AfCad files installed with the scenery and see if the CTD's stop. If it runs OK then the file or files needs checking for errors with the AfCad 2 program. Of course it could be something else but try that first.