Thanks for this nice mod, which also works great in version 4.0.12 !
In my cart.php I found the code that must be replaced at line 709 and it had one extra line, which I didn't replace with the new code.
Code:
elseif ($mode=="order_message") {
$smarty->assign("main","order_message");
$smarty->assign("mode","order_message");
include $xcart_dir."/include/increment.php";
$location[] = array(func_get_langvar_by_name("lbl_order_processed"), "");
Thanks again!