I'm sorry, but I tried it again, with FSX-SE, no problems whatsoever.
Have you see a request from the sim to trust the two updated files (Addon Manager and Couatl ) ? If you haven't seen any request, that's almost certain the problem is the antivirus, which blocked the files before they even start to run.
If got the request, have you replied Yes to it ?
If you don't remember, do this:
- Uninstall something from FSDT, like GSX, and reply YES to the question "Do you want to remove the Addon Manager ?"
- Reinstall GSX.