Using version 1.3.9f. When the button is clicked I get the following message instead of an item being added to the cart.
" Error 404 - Not found
Your browser can't find the document corresponding to the URL you typed in."

Here is the link shown at the bottom of the browser when I highlight the button.

"mystore/index.php?main_page=product_info&cPath=612_613_614&products_id=13380&action=add_ product"
which looks correct to me compared to another active site I have.

so far I have checked the files and filesizes of the working store against this one and all files containing "shopping_cart" are there and are the same size.

Any help would be greatly appreciated.
thanks,