Coupon not being reflected in payments

[nlim3482]

I am using Zen cart 1.3.8a

I have Paypal IPN - website payments standard and a third party payment module (iPayBy) installed.

When a customer enters a coupon, the new total is being correctly updated in the checkout page however it is not being reflected in the actual payments that I receive

eg. an item for $100 with a 10% discount coupon is correctly being reflected as $90 in the checkout page but when the CC payment is put through Paypal or the third party payment module, the total amount ends up being $100 (the coupon hasn't been applied)

Is this a bug or am I missing a step somewhere?

[DrByte]

I can't replicate that problem when using a fresh clean uncustomized install of v1.3.8a or v1.3.9d, using PayPal Website Payments Standard or COD or Check/MoneyOrder or Linkpoint API or Authorize.net AIM modules.