$_POST var for 'add to cart' form on flypage

Hey guys, great script!! I tried to do my project with osCommerce at first but found that the way the HTML was embedded made it too hard to have control over the markup. I love the way this is organized and laid out. I've been able to put everything into a pre-designed site layout and make it work how I want. Kudos!!

The problem I'm having is that after rearranging flypage.ihtml to fit the content into my CSS layout, filling out the quantity field and submitting the addCart form just inserts a blank line with a quantity of zero and no product into the shopping cart. Adding an item to the cart still works from the links created by the show_snapshot() function.

What I'm trying to figure out is which file includes the function that processes the $_POST variables created by that form on flypage.ihtml. How do I follow that data all the way to the shopping cart so I can find where I went wrong?

Thanks for any help you guys may be able to give me. Again, great script (until I screwed it up)!