try changing line 2-5 of the checkout_failure.php page:
if (!empty($_SERVER['HTTPS'])) {
header("location: http://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI']);
die();
}
to:
/*if (!empty($_SERVER['HTTPS'])) {
header("location: http://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI']);
die();
}*/