a bit old this thread but I am getting this too when using this mod.

In edit_orders.php on lines 185 and 186 the fields for customer email address ( and name and date_purchased) are wrong.

Notice the $check_status['customers_email_address'] should be $check_status->fields['customers_email_address'].

Wrong code:-
Code:
$email = STORE_NAME . "\n" . EMAIL_SEPARATOR . "\n" . EMAIL_TEXT_ORDER_NUMBER . ' ' . $oID . "\n" . EMAIL_TEXT_INVOICE_URL . ' ' . zen_catalog_href_link(FILENAME_CATALOG_ACCOUNT_HISTORY_INFO, 'order_id=' . $oID, 'SSL') . "\n" . EMAIL_TEXT_DATE_ORDERED . ' ' . zen_date_long($check_status['date_purchased']) . "\n\n" . $notify_comments . sprintf(EMAIL_TEXT_STATUS_UPDATE, $orders_status_array[$status]);
zen_mail($check_status['customers_name'], $check_status['customers_email_address'], EMAIL_TEXT_SUBJECT, $email, STORE_OWNER, STORE_OWNER_EMAIL_ADDRESS);
Correct Code:-
Code:
$email = STORE_NAME . "\n" . EMAIL_SEPARATOR . "\n" . EMAIL_TEXT_ORDER_NUMBER . ' ' . $oID . "\n" . EMAIL_TEXT_INVOICE_URL . ' ' . zen_catalog_href_link(FILENAME_CATALOG_ACCOUNT_HISTORY_INFO, 'order_id=' . $oID, 'SSL') . "\n" . EMAIL_TEXT_DATE_ORDERED . ' ' . zen_date_long($check_status->fields['date_purchased']) . "\n\n" . $notify_comments . sprintf(EMAIL_TEXT_STATUS_UPDATE, $orders_status_array[$status]);
zen_mail($check_status->fields['customers_name'], $check_status->fields['customers_email_address'], EMAIL_TEXT_SUBJECT, $email, STORE_OWNER, STORE_OWNER_EMAIL_ADDRESS);