Did as recommended - no luck - still the same couatl engine error.
Your log seems to indicate the problem is either your antivirus, or you haven't downloaded and installed the latest GSX because, your Couatl version reported in the log shows it's version 3829, which is several months old.
Assuming you are entirely sure you are downloading the latest GSX installer, and you are installing *that* one, the only possible explanation is the antivirus is preventing the installation of the latest Couatl (which of course is included in the installer).
- Uninstall GSX. Reply YES to the question "Do you want to remove the Addon Manager ?". This will remove everything from the old version.
- Disable the antivirus
- Be sure you are installing GSX using the *latest* installer
- Reinstall GSX.
- Configure the antivirus to exclude the Addon Manager folder from scanning.