Thread:Extension talk:GoogleAppsAuthentification/403 Forbidden error upon return

I installed and set up the extension.

When I try to login, I'm redirected to the Google login page (first time to my domain login page, but on later test to the standard login... nevermind, that's not the problem now).

I'm then asken to authorize mi URL site. Everything looks good so far.

But when I'm supposed to return to the site I get this:

Forbidden You don't have permission to access /wiki/Especial:Entrar on this server. Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request. (the "Especial:Entrar" is because the site is in spanish)

or

Forbidden You don't have permission to access /index.php on this server. Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Depending on the URL I use.

I set the 777 permission to the whole extension folder and its child files/folder. Just in case. Any idea?