Hi all, I installed this for a client who also has the order editor plugin. It failed in one spot, line 129. It was assuming there would be a cart and an order object, but in this case, there is no cart. This is the simple fix:
Change line 129 of catalog/includes/modules/shipping/fedexwebservices.php from:
$totals = $order->info['subtotal'] = $_SESSION['cart']->show_total();
to
$totals = $order->info['subtotal'] || $_SESSION['cart']->show_total();
HTH,
-Bill