problem with extern.php after having updated to 1.2

Hi,

I've just updated my forum. All works good except extern.php which worked good with 1.1.5
in my page I got this code to call extern:

<?php
$ancien_get_action = $_GET['action'];
$ancien_get_show = $_GET['show'];
$_GET['action'] = 'active';
$_GET['show'] = 8;
include($_SERVER['HTTP_RACINE'] . '/forum/extern.php');
$_GET['action'] = $ancien_get_action;
$_GET['show'] = $ancien_get_show;
?>

I now get the message "The file 'config.php' doesn't exist or is corrupt. Please run install.php to install PunBB first."

when I try to go directly on extern.php by http://www.pluriservices.net/forum/extern.php , it gives me that error "No parameters supplied. See extern.php for instructions."

Can you help to make extern.php work?
has extern.php been modified from 1.1.5 to 1.2 ?

Thanks for your help.

Ludo,