on the confirm cart page, change:
<?php
@session_start();
if (isset($_POST["CheckoutWizard_submit"]) || isset($_POST["CheckoutWizard_submit_x"])) {
WA_persistForm("session","CheckoutWizard_NewFromBlank_Default",0,"/","");
}
?>
to:
<?php
@session_start();
if (isset($_POST["CheckoutWizardBilling_submit"]) || isset($_POST["CheckoutWizardBilling_submit"])) {
WA_persistForm("session","CheckoutWizardBilling_NewFromBlank_Default",0,"/","");
}
?>


