for the error message you report, see the following thread:
I notice on your page that you have two eCart objects:
the add to cart behavior is set to add the items to the henkor_cart eCart object.
what ecart object is being used by the cart display page, make sure that the cart display is created to use the same eCart object as the add to cart button on the result page, the henkor_cart object. I suspect that the cart display is for the other cart object.