title: Magento Add to cart button redirects back to product page, but only for certain products
body: <p>I have 3 products on my site.  Two of them can be added to cart just fine.  The third one, when clicking add to cart, redirects back to the product page without adding the product to the cart.  The other two, when clicked, directs to the cart page, showing the item in the cart.   I'm baffled.   Where should I look to fix this? </p>