PayPal IPN - Website Payments Standard

Not sure what's up here.

Using this payment mod, works ok with a sale.
If I attempt to use a gift certificate, the price rockets up in price.

On an item of 199.99 plus taxes and shipping, total is $237.51.
This amount is correct.

If I apply a gift certificate of $-25.41, my total is go up to $396.84
Math is out of wack here.

With the Paypal Express Checkout, gift certificates worked great, but I screwed up this and waiting for help finding the 56 character sig code.


None the less, this payment module seems to not working properly.