Got a warning message when accessing forum with a non logged user.
warning: file_exists() [function.file-exists]: open_basedir restriction in effect. File(sites/all/modules/advanced_forum/styles/blue_lagoon_stacked/images/vous-devez-vous-identifier-ou-créer-un-compte-pour-écrire-des-commentaires.png) is not within the allowed path(s): (D:/Apache Web Site/Aquaforum/aquaforum2.org) in D:\Apache Web Site\Aquaforum\aquaforum2.org\sites\all\modules\advanced_forum\advanced_forum.module on line 1287.

The unparsed code in the path correspond to a french message appearing at the top of the topic.
Advanced forum try to parse this message in a image name... and fail.

After tracking:
the faultive parsing come from the _advanced_forum_buttonify_links function, in the default statement of the switch.

default:
          // Attempt to buttonify by key name.
          // debug : working statement that try (and fail) to find a picture
          $image = advanced_forum_theme_image($link_key . '.png', $link['title']);
          if (!$image) {
            // If no luck there, try the adjusted title.
            // debug : This fail to pars text contening url
            $title = strtolower(str_replace(' ', '-', $link['title']));
            // debug : this generate the error
            $image = advanced_forum_theme_image($title . '.png', $link['title']);
            }
          if ($image) {
            // If we found an image, use it. Otherwise leave the title alone.
            $links[$link_key]['title'] = $image;
            $links[$link_key]['html'] = TRUE;
          }

The text that creat this error :
vous devez vous identifier ou créer un compte pour écrire des commentaires
vous devez <a-href="/fr/user/login?destination=comment%2freply%2f10205%23comment-form">vous identifier</a> ou <a-href="/fr/user/register?destination=comment%2freply%2f10205%23comment-form">créer un compte</a> pour écrire des commentaires

workaround : commented the faulty code part