Just installed today on my zen cart 1.5.7 (1.5.7, not 1.5.7a or 1.5.7b). I found that the subtotal does not change at all no matter how I add or remove products. But after I removed all the products, and then add new products to the order, all the calculation becomes right. It seems that the products already in the order are ignored in calculation

Another problem is: when I use "reset totals prior to update", subtotal becomes 0, and does not change anymore, no matter how I add/remove products

Really strange...