--- payment.142.module	2006-02-26 17:29:22.000000000 -0600
+++ payment.module	2006-02-26 17:30:14.000000000 -0600
@@ -70,7 +70,7 @@
         form_set_error('payment_method', t('Please choose a payment method.'));
       }
       else {
-        module_invoke($txn->payment_method, 'paymentapi', $txn, 'on checkout');
+        module_invoke(payment_get_modulename($txn->payment_method), 'paymentapi', $txn, 'on checkout');
       }
       break;