Umberto, apologies, but I think you've confused me with a poster from another thread. For one thing, I (unfortunately) never managed to install Couatl 3 with no errors...
I've had two separate error messages, but not the ones you've mentioned here. The first one is "addon X is out-dated." The second one is "could not find valid AFCAD."
To be totally clear, here's exactly what I did.
1) I first put in the exceptions you identified in my antivirus and then disabled it entirely.
2) I downloaded the latest full addon manager and the Couatl 3 beta.
3) I first reinstalled the latest full addon manager (which as I understand it means Couatl 2 was reinstalled), mostly to make sure I could "roll back" to that without complications if needed.. After doing this GSX worked as it did before (that is, mostly normally but incapable of restarting in FSX: SE and prone to crashes).
4) I then installed the Couatl 3 beta.
5) I then reactivated my antivirus.
6) When running FSX after that, on a flight fully loading I'd get a serious of dialog box error messages, one for each FSDT/Flightbeam scenery I have installed (all of them, in fact), that read "The addon 'X' is out-dated. Please download and install the latest Stand-Alone Addon Manager." It then minimized FSX and opened the addon manager download page.
7) When I ignored that and tried to use GSX services anyway after restoring FSX, I got the "could not find AFCAD" message at the top of the screen. I tried this at several airports, all with the same result.
I then reinstalled using the latest full addon manager, which restored the old functionality--which, to be clear, is not ideal (since it crashes often and can't be reset), but still works maybe 70% of the time instead of 0%.
I hope that helps clarify. Thanks for your help.
Best,
James