Due to the changes in EU law that came in a short while ago, EU law now requires that VAT be charged at the rate of the country that you are buying from. It also requires that sellers collect two pieces of “non-conflicting” information to verify their location. This is normally handled in the background by the shopping cart.
The problem occurs if you’re billing address is in one country and you are currently located in another. Because the law requires you to provide two pieces of information, the system will ask you to verify your location. This is to comply with EU law.