When an item isn't removed from the inventory it usually means the remote calls at Mal's aren't setup correctly. Also check to make sure you have a Paypal Business account, rather than a Personal account (or upgrade from Personal). Personal accounts can be used with the cart, but the inventory control and order tracking will not work!
1. Log in to Mals http://mals-e.com
2. Click "Cart Setup"
3. Choose the "Remote Calls" link right hand column
4. Make sure the box reads: IPnumber/~your_cpanel_user_name/go/finish.php
(Note: be sure to use YOUR Ip number and cpanel user name - not the one in the example above)
8. Under 'Website Standard', select the second option: 'return the customer back to the cart. See the notes below...'.