Thanks Ray. The error message is now gone and the checkout_failure.php page loads correctly as I wanted it. But the notification email still does only include the information that are stored in eCart such as <?php echo $eCart1->DisplayInfo("Name"); ?> for example. The information that are entered in the checkout form such as customer name, phone number etc. (<?php echo(WA_getSavedFormValue('CheckoutWizard_Basic_Default','First_Name')); ?>) is still blank. Is there any way of including this into the confirmation email too?
Thanks again for your help.