Problem in checkout confirmation step

I was trying to sort out the problem with one of the payment module.
For my local install, when I said (in the file includes\templates\template_default\templates\tpl_checkout_confirmation_default.php)
echo "$form_action_url";
I get the value as
https://secure.authorize.net/gateway/transact.dll

When I tried to do with one of the live site
I get the value of $form_action_url as

which is different from what was supposed to be
https://gateway.usight.com/postauth.secure
(taken from https://gateway.usight.com/post_auth.jsp)
So I assigned $form_action_url="https://gateway.usight.com/postauth.secure" just to test if it starts working but after the checkout it asks to download the file postauth.secure containing all the info which is getting passed

Sample info which I am getting is

<form name="checkout_confirmation" action="https://urltomysite/index.php?main_page=checkout_process&zenid=4903780f82614bad49351ff0957380ac" 
method="post" id="checkout_confirmation" onsubmit="submitonce();">
<input type="hidden" name="GWUsername" value="user" />
<input type="hidden" name="GWCardNumber" value="4111111111111111" />
<input type="hidden" name="CVV2" /><input type="hidden" name="GWCardExpMonth" value="01" />
<input type="hidden" name="GWCardExpYear" value="2007" />
<input type="hidden" name="GWAmount" value="20.45" />
<input type="hidden" name="Email" value="[email protected]" />
<input type="hidden" name="GWBillingFirstName" value="Steve" />
<input type="hidden" name="GWBillingLastName" value="Ryden" />
<input type="hidden" name="GWNameOnCard" value="Steve Ryden" />
<input type="hidden" name="GWBillingAddress" value="234, Blue Park" />
<input type="hidden" name="GWBillingCity" value="Florida" />
<input type="hidden" name="GWBillingState" value="NA" />
<input type="hidden" name="GWBillingZip" value="34664" />
<input type="hidden" name="GWBillingCountry" value="US" />
<input type="hidden" name="Phone" value="7898278936" />
<input type="hidden" name="InvoiceNo" value="slf20061114123022" />
<input type="hidden" name="Description" value="Order Submitted from IP:" />
<input type="hidden" name="Customer_id" />
<input type="hidden" name="zenid" value="4903780f82614bad49351ff0957380ac" />
<div class="buttonRow forward">
<input type="image" src="includes/templates/farm/buttons/english/button_confirm_order.gif" alt="Confirm Order" title=" Confirm Order " name="btn_submit" id="btn_submit" /></div>
</form>

These values indicate that usight.php has been used and these variables are getting passed

Few questions:

1. Is this the correct approach to handle this situation?
2. Where does the variable $form_action_url gets its value from and why is it not automatically picking up https://gateway.usight.com/postauth.secure

Thanks for the help

Fine, I have been successful in redirecting to the payment gateway but after the transaction is over and GWReturnURL=return page is shown, my cart doesnt gets empty
What might be causing this?
I know that it goes to header_php.php in checkout_process which looks fine to me

<?php
/**
 * Checkout Process Page 
 * 
 * @package page
 * @copyright Copyright 2003-2006 Zen Cart Development Team
 * @copyright Portions Copyright 2003 osCommerce
 * @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
 * @version $Id: header_php.php 2978 2006-02-07 00:52:01Z drbyte $
 */ 

  require(DIR_WS_MODULES . zen_get_module_directory('checkout_process.php'));

// load the after_process function from the payment modules
  $payment_modules->after_process();

  $_SESSION['cart']->reset(true);

// unregister session variables used during checkout
  unset($_SESSION['sendto']);
  unset($_SESSION['billto']);
  unset($_SESSION['shipping']);
  unset($_SESSION['payment']);
  unset($_SESSION['comments']);
  $order_total_modules->clear_posts();//ICW ADDED FOR CREDIT CLASS SYSTEM

  zen_redirect(zen_href_link(FILENAME_CHECKOUT_SUCCESS, '', 'SSL'));

  require(DIR_WS_INCLUDES . 'application_bottom.php');
?>

Please help

Anyone please help?

Hi, I've also been looking at / editing all these files and they're really tricky. Your code looks fine to me, so I can't imagine what the problem is. I hope you get it sorted somehow. Best idea I can think of: re-upload all the files that could be causing the problem and start over (i've done that so many times!)

Are you using POST or GET requests when doing the transaction is being processed?

Also got a link I can look at with a test product maybe?

Rob