Hello,
I recently ran into a problem.
I was testing Paypal IPN, and when I was going through the process of paying, the amount on the invoice showed $0.00, and didn't show the total of their order that was placed through zen cart.
I'm also having a problem with Paypal IPN, where when somebody uses an e-check to pay me with, and the checkout all the way, there order doesn't show up in the "Order Totals" section of the admin.