Index: includes/commerce_authnet.admin.inc
===================================================================
--- includes/commerce_authnet.admin.inc	(revision 1438)
+++ includes/commerce_authnet.admin.inc	(working copy)
@@ -257,7 +257,16 @@
   $payment_method = $form_state['payment_method'];
 
   // Determine the last 4 credit card digits from the previous transaction.
-  $transaction_payload = end($transaction->payload);
+  foreach($transaction->payload as $transaction_id => $payload) {
+    if($payload[0] == 1 && !empty($payload[50])) {
+      $transaction_payload = $payload;
+      break;
+    }
+  }
+  
+  if(!isset($transaction_payload)) 
+    $transaction_payload = end($transaction->payload);
+  
   $credit_card = !empty($transaction_payload[50]) ? substr($transaction_payload[50], 4, 8) : '';
 
   // Make sure that the last 4 digits are available and valid.
@@ -311,10 +320,8 @@
       if ($response[2] == 54) {
         drupal_set_message(t('The transaction must be setted before a credit can be issued. This usually takes 24 hours'), 'error');
       }
-
       commerce_payment_transaction_save($transaction);
     }
   }
-
   $form_state['redirect'] = 'admin/commerce/orders/' . $order->order_id . '/payment';
 }