--- uc_paypal/uc_paypal.module.orig	2010-08-12 03:52:20.000000000 +1000
+++ uc_paypal/uc_paypal.module	2011-10-07 13:08:02.000000000 +1100
@@ -404,9 +404,29 @@
     }
   }
 
+  //
+  // DEBUG.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_wpp_charge: calling uc_paypal_api_request with:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_request)));
+  }
+
+  //
+  // send request.
+  //
   $nvp_response = uc_paypal_api_request($nvp_request, variable_get('uc_paypal_wpp_server', 'https://api-3t.sandbox.paypal.com/nvp'));
   $types = uc_credit_transaction_types();
 
+  //
+  // DEBUG.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_wpp_charge: response from uc_paypal_api_request:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_response)));
+  }
+
+  //
+  // process response.
+  //
   switch ($nvp_response['ACK']) {
     case 'SuccessWithWarning':
       watchdog('uc_payment', '<b>@type succeeded with a warning.</b>!paypal_message',
@@ -691,13 +711,37 @@
     unset($nvp_request['ADDROVERRIDE']);
   }
 
+  //
+  // DEBUG: request.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_checkout: calling uc_paypal_api_request with:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_request)));
+  }
+
+  //
+  // send request.
+  //
   $nvp_response = uc_paypal_api_request($nvp_request, variable_get('uc_paypal_wpp_server', 'https://api-3t.sandbox.paypal.com/nvp'));
 
+  //
+  // DEBUG: response.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_checkout: response from uc_paypal_api_request:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_response)));
+  }
+
+
+  //
+  // error
+  //
   if ($nvp_response['ACK'] != 'Success') {
     drupal_set_message(t('Error message from PayPal:<br />@message', array('@message' => $nvp_response['L_LONGMESSAGE0'])), 'error');
     drupal_goto('cart/checkout');
   }
 
+  //
+  // success
+  //
   $_SESSION['TOKEN'] = $nvp_response['TOKEN'];
 
   if (strpos(variable_get('uc_paypal_wpp_server', 'https://api-3t.sandbox.paypal.com/nvp'), 'sandbox') > 0) {
@@ -769,8 +813,44 @@
   $order->products = $items;
   uc_order_save($order);
 
+  //
+  // DEBUG: request.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_form_submit: calling uc_paypal_api_request with:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_request)));
+  }
+
+  //
+  // send request.
+  //
   $nvp_response = uc_paypal_api_request($nvp_request, variable_get('uc_paypal_wpp_server', 'https://api-3t.sandbox.paypal.com/nvp'));
 
+  //
+  // DEBUG: response.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_form_submit: response from uc_paypal_api_request:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_response)));
+  }
+
+  //
+  // unknown error.
+  //
+  if (!$nvp_response || !isset($nvp_response['ACK'])) {
+    drupal_set_message(t('Error:<br />uc_paypal_ec_form_submit: uc_paypal_api_request() returned unknown response'), 'error');
+    drupal_goto('cart/checkout');
+  }
+
+  //
+  // failure.
+  //
+  if ($nvp_response['ACK'] != 'Success') {
+    drupal_set_message(t('Error message from PayPal:<br />@message', array('@message' => $nvp_response['L_LONGMESSAGE0'])), 'error');
+    drupal_goto('cart/checkout');
+  }
+
+  //
+  // success.
+  //
   $_SESSION['cart_order'] = $order->order_id;
   $_SESSION['TOKEN'] = $nvp_response['TOKEN'];
 
@@ -839,11 +919,50 @@
     'CURRENCYCODE' => variable_get('uc_paypal_wpp_currency', 'USD'),
   );
 
+  //
+  // DEBUG: request.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_submit_form_submit: calling uc_paypal_api_request with:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_request)));
+  }
+
+  //
+  // send request.
+  //
   $nvp_response = uc_paypal_api_request($nvp_request, variable_get('uc_paypal_wpp_server', 'https://api-3t.sandbox.paypal.com/nvp'));
 
+  //
+  // DEBUG: response.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_submit_form_submit: response from uc_paypal_api_request:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_response)));
+  }
+
+  //
+  // unknown error.
+  //
+  if (!$nvp_response || !isset($nvp_response['ACK'])) {
+    drupal_set_message(t('Error:<br />uc_paypal_ec_submit_form_submit: uc_paypal_api_request() returned unknown response'), 'error');
+    drupal_goto('cart/checkout');
+  }
+
+  //
+  // failure.
+  //
+  if ($nvp_response['ACK'] != 'Success') {
+    watchdog('uc_paypal', 'Request of IPN transaction FAILED: @message', array('@message' => $nvp_response['L_LONGMESSAGE0']));
+    drupal_set_message(t('Error message from PayPal:<br />@message', array('@message' => $nvp_response['L_LONGMESSAGE0'])), 'error');
+    drupal_goto('cart/checkout');
+  }
+
+  //
+  // success.
+  //
   unset($_SESSION['TOKEN'], $_SESSION['PAYERID']);
   $_SESSION['do_complete'] = TRUE;
 
+  watchdog('uc_paypal', 'Request of IPN transaction succeeded.');
+
   $form_state['redirect'] = 'cart/checkout/complete';
 }
 
@@ -1242,3 +1361,12 @@
 function _uc_paypal_currency_array() {
   return drupal_map_assoc(array('AUD', 'BRL', 'CAD', 'CHF', 'CZK', 'DKK', 'EUR', 'GBP', 'HKD', 'HUF', 'ILS', 'JPY', 'MXN', 'MYR', 'NOK', 'NZD', 'PHP', 'PLN', 'SEK', 'SGD', 'THB', 'TWD', 'USD'));
 }
+
+function _print_r_to_string($object) {
+  ob_start();
+  print_r($object);
+  $string = ob_get_contents();
+  ob_end_clean();
+
+  return $string;
+}
--- uc_paypal/uc_paypal.pages.inc.orig	2011-10-07 13:18:21.000000000 +1100
+++ uc_paypal/uc_paypal.pages.inc	2011-10-07 12:53:55.000000000 +1100
@@ -171,8 +171,33 @@
     'TOKEN' => $_SESSION['TOKEN'],
   );
 
+  //
+  // DEBUG.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_review_redirect: calling uc_paypal_api_request with:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_request)));
+  }
+
+  //
+  // send request.
+  //
   $nvp_response = uc_paypal_api_request($nvp_request, variable_get('uc_paypal_wpp_server', 'https://api-3t.sandbox.paypal.com/nvp'));
 
+  //
+  // DEBUG.
+  //
+  if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+    watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_review_redirect: response from uc_paypal_api_request:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_response)));
+  }
+
+  //
+  // error
+  //
+  if ($nvp_response['ACK'] != 'Success') {
+    drupal_set_message(t('Error message from PayPal:<br />@message', array('@message' => $nvp_response['L_LONGMESSAGE0'])), 'error');
+    drupal_goto('cart/checkout');
+  }
+
   $_SESSION['PAYERID'] = $nvp_response['PAYERID'];
 
   drupal_goto('cart/checkout/review');
@@ -194,8 +219,36 @@
       'TOKEN' => $_SESSION['TOKEN'],
     );
 
+    //
+    // DEBUG: request.
+    //
+    if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+      watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_review: calling uc_paypal_api_request with:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_request)));
+    }
+
+    //
+    // send request.
+    //
     $nvp_response = uc_paypal_api_request($nvp_request, variable_get('uc_paypal_wpp_server', 'https://api-3t.sandbox.paypal.com/nvp'));
 
+    //
+    // DEBUG: response.
+    //
+    if (variable_get('uc_paypal_wps_debug_ipn', FALSE)) {
+      watchdog('uc_paypal', 'DEBUG: uc_paypal_ec_review: response from uc_paypal_api_request:<pre>@debug</pre>', array('@debug' => _print_r_to_string($nvp_response)));
+    }
+
+    //
+    // error
+    //
+    if ($nvp_response['ACK'] != 'Success') {
+      drupal_set_message(t('Error message from PayPal:<br />@message', array('@message' => $nvp_response['L_LONGMESSAGE0'])), 'error');
+      drupal_goto('cart/checkout');
+    }
+
+    //
+    // success.
+    //
     $_SESSION['PAYERID'] = $nvp_response['PAYERID'];
 
     $shipname = check_plain($nvp_response['SHIPTONAME']);