on your pages, find the follpowing code and change it to:
<?php
// WA eCart Redirect
if ($lesfutons_fr->redirStr != "") {
header("Location: ".$lesfutons_fr->redirStr);
}
?>
and change it to:
<?php
// WA eCart Redirect
if ($lesfutons_fr->redirStr != "") {
session_commit();
header("Location: ".$lesfutons_fr->redirStr);
}
?>
it could something in the web.config file causing a conflict, try deleting that file from the server.
if the pages work remotely, but not online, there is something on the remote server that is causing it to break.