Error if balance is 0 or less when submitting

using powerstore 4.5 I am using PayPal Payments Pro and am getting errors when my total is 0 or less using a coupon or if product is 0 either accepting credit cards or paypal. Orders work to success if the total is 0+. This happens before adding any shipping charges. Why would I do this? I want to give away some of my product for free for first time buyers with users only paying shipping and/or have the coupon affect the total in addition with shipping.
if you buy an item $13 or less using coupon test01 I get the following error messages.

error message using paypal:

Ancestral Quest101182Discount-1310Authorization **********.ECO_Auth_Request.***** 2011-12-10T20:59:19ZFailure45af0ac3927a5Invalid DataThis transaction cannot be processed. The amount to be charged is zero.10525ErrorInvalid DataItem total is invalid.10426Error63.02271164

accepting credit cards on checkout debug error message:

79071.199.60.58gecqvn92qq1odqbki5lavoti37" ["PP_DirectPayment"]=> string(2114) "2011-12-10T00:11:17ZFailure13fe88db6250bInvalid DataItem total is invalid.10426Error59.022786583.27"

my website still under construction is www.genealogywallcharts.com.

is there a fix for this or do I always have to charge customers for a product? Thanks....

Hey Doug,

Sadly, your order total must be greater than 0 for PayPal to succeed. The solution is to charge only 1 cent for things you want to give away, and PayPal will be happy.

If you have any more questions, please don't hesitate to ask.