Our Magento Based ecommerce site (ver 1.7.0.2) is having issues with some of our customers trying to checkout with an invalid zip code.It defaults to "No Shipping Required" and has 'In Store Pick-up' as the only method available... Customers are submitting orders using this and causing problems on our end.We need it to display some text or an alert letting them know when this exact problem occurs.We are also using FireCheckout as our onepage cart extension that doesn't seem to display any error message either, just like magento's default cart. Thank you,Mitchell