Thanks jason. I have implemented a two zone (based on zip code) shipping cost. Briefly, I added two fields to the product table in the database, one for each zone (roughly east or west of the Mississippi). Every product has two shipping costs, one which is ultimately used based on the buyers zip code. I have modified the shopping cart so the buyer can enter their zip code. I have also entered in conditional statements (based on zip code) on the cart and confirm pages that determine and calculates the shipping cost per product added to the cart, the total shipping cost, and the grand total (products+tax+shipping), with the help of functions I added to the eCart definition page. The cart and confirm pages work fine, it is when I go to check out that I see the above problem. I expected to see some kind of problem based on my changes so far, and hoped that you would confirm the origin of the problem.
I have not gutted any of the original shipping code, but I expect that leaving it there will not cause problems, since that part of the store is not set up (i..e. without the real time shipping quotes), those variables should have no value. I have just added my own code for shipping and brought those values into the equations. The reason I am not using the pre-built shipping function is the seller has already used a similar zone shipping system, and feels it works best for his types of products (large and heavy).
Based on your response, I will attempt to carry my changes forward until I get a "sale" authorization confirmation. With the new ticket system, I am not sure if you can continue helping me within the forum format since this is clearly not an as-is implementation.
However, please let me know if my assumptions about the pre-built shipping code are incorrect.