Like the last time, I reinstalled everything in the exact order you advised and XPOI, GSX and Couatl are working again.
Of course they do, that's why I said to do it.
Now - how do we find out why this has happened twice and how to stop it from occuring again?
If will only happen if you install an older version of XPOI using an older installer, and forget to reinstall the Stand-Alone Addon Manager after it.
If you use the current XPOI installer, there's shouldn't be any need to update the Stand-Alone Addon Manager installer after the installation.