Well, actually I just made another test of installation, with the assumption I guess you also made : taking care of not having "GSX" in folder path... and it worked !
Indeed previously, when "GSX" was part of the installation folder path, the "Couatl Live Update" program launched at the end of the installation was actually removing lot of files automatically...!
That is not the case anymore.
So now the working installation path is "
D:\FSDT\Addon Manager" : no "GSX" anymore in folder path, which seems to create the issue reported by the people in that thread.
