I got also error messages after upgrade from 2.0.6 to 2.0.8e
When trying to add some products to shopping cart following error messages will appear:
"Error the quantity of the product for calculation is 0, please notify the shopowner, the product id 0"
In my test computer version 2.0.8e shopping cart works fine but when updated my live site I got same error message with every product what I tried to add my cart.