I know this is an old post, but I just recently bought Patrician 3, and had this problem. I run Windows 7 Professional 64 Bit, and could not get the editor to open for me. If you click the start menu icon, it will give this error. However, I was able to open it by going to the actual game folder and opening it from there. On my system it was "C:\Program Files (x86)\GOG.com\Patrician 3" and yours may be different depending on your system and where you installed the program. I hope this helps for anyone else that encounters this problem.