I am having Intermittently an issue with orders paid via paypal, but no data inserted to zen_orders and no mail sent to customers. Usually when I try to order myself, all works fine.

The only clue I got is a debug message :


[19-jan-2010 14:32:56] PHP Fatal error: Call to a member function add() on a non-object in /home/content/m/i/n/mineralz/html/includes/classes/order_total.php on line 75

I can't see anything special in this file, nor I understand why it's called during checkout, that AFAIK uses URL like : index.php?main_page=checkout_process&referer=paypal&tx=123qwe123qwe123qwe&st=Com pleted...

I'm using Zen Cart 1.3.8a
PHP Version 5.2.8
GoDaddy Shared Linux hosting (with appropriate changes for godaddy applied to paypal ipn)

Any ideas ?