Change country on order problem. PopUp works blank

-- url of the page with the problem -- : photostore.andreasuriani.com
-- HikaShop version -- : Business
-- Joomla version -- : 3

Hi All,
i've this problem:

After registration, when u try to do an order and input your billing address (Italy is default), when i change country, it show a blank page with dropdown menu and nothing else! The order dosn't proceed!

It's a very big problem!!!
Why this?

Look image attachment:
1) Try to select France
2) The result after click

nobody can help me??

Hi,

Your website is in maintenance so I'm not able to see the problem.

This looks like some kind of javascript error but we would have to be able to look at the page to find out what's going on.