Good question... I dunno what is the answer to that question. I'll do some investigation and get back to you if I find an good answer. You should email the people at iPage as they probably could answer your iPage question..
I have the exact same problem, except I am using the sts template system and want to add to cart from my category page rather than go to the product info page. THIS HAS SOLVED MY PROBLEM, THANK YOU, THANK YOU, THANK YOU!! I have actually been struggling with this for a while and have been close, but this has provided the missing link, and that is my Final Answer!!!..
Using that took me to the product_info.php page. It did not add the product to the cart.
Double check your link, you should be linking to the shopping_cart.php file, not product_info.php file. Otherwise I am not sure what is causing the problem. This seems to work good for me. Let me know, thanks...
I have a button in a flash swf that when I click it it takes me to product_info.php. The link is correct by linking to shopping_cart.php..