Smiley,
Try connecting the External Dispatcher after logging into the server. Once you log in you will probably have to check the Allow External DS option again. Even if you are connected before you logon, it will disconnect you anyway once you are on a server in my experience.
You shouldn't need to load all the routes before connecting. The host indicates the routes that are used and are loaded automatically when you come online.
Try to follow these steps when loggin on the server
1. Open the Run 8 program
2. Select Route/Train
3. Run Simulator (no need to select any train, routes or world when logging into a server)
4. Once simulator loads, go to F1 client tab and log onto network
5. Go to F1 options tab and select Allow External DS
6. F4 to put simulator in Window mode, minimize and the open your External Dispatcher program. It should automatically connect at this point.
This is the method that I use and it seems to work for me.
Good luck!
Mike