on your page, do a find and replace to hcange:
$_SERVER["../PHP_SELF"]
to:
$_SERVER["PHP_SELF"]
and change:
$ATC_RedirectAfter = "../../cart.php";
$ATC_RedirectAfter = "../../cart.php";
to:
$ATC_RedirectAfter = "../../cart.php";
$ATC_RedirectIfIn = "../../cart.php";