I apologize for the delay in responding to your forum post.
I checked your site and was unable to reproduce the problem. Barbados, like Ireland would have no problem adding in a shipping amount as neither country has postal codes. Any country with postal codes needs an appropriate postal code entered in for shipping to be added to the cart.
So you know I did send you a reply to your e-mail from the 19th about this issue. It is possible that my e-mail is in your Spam/Junk folder.