When using Netbilling's latest payment module in combination with various discount modules (discount_quant_v1, qty_discount_v1.41, etc), the discounted price is not sent to the gateway.
This can be fixed by simply replacing the following lines in checkout_process.php:
// load the before_process function from the payment modules
$payment_modules->before_process();
require(DIR_WS_CLASSES . 'order_total.php');
$order_total_modules = new order_total;
$order_totals = $order_total_modules->process();
With following:
// load the before_process function from the payment modules
// $payment_modules->before_process();
require(DIR_WS_CLASSES . 'order_total.php');
$order_total_modules = new order_total;
$order_totals = $order_total_modules->process();
// load the before_process function from the payment modules
$payment_modules->before_process();
I hope this helps anybody else that runs across this issue.