Our store (as do many others) pings usps.com with your address in order to determine shipping cost to your location. You'll get the message saying that you'll be contacted for shipping costs if we're unable to contact usps.com.
Rather than preventing you from ordering, it instead says that you can order, but that we'll contact you later. If this has happened to you, we have either contacted you, or will contact you before we ship.
If you see this message, and would rather wait to place your order, then try again every few minutes.