Address pop-up window

I've noticed that when I try to edit my address or add a new address on my Customer Account page, which is a link to the HikaShop User Details menu item, the i-frame doesn't act as a pop-up like it should. Instead, it pushes the i-frame below the footer.

Here's the source:
<a href="#" id="hikashop_new_address_popup" onclick="window.hikashop.openBox(this,null,true); return false;"><span class="icon-32-new" title="New"></span>New</a><div class="modal hide fade" id="modal-hikashop_new_address_popup" style="width:780px;height:570px;margin-left:-390px">

The page is the-authors-club.com/index.php/login-to-...omer-account/address (Main menu > Customer Account > Manage Your Addresses. It does it both in Internet Explorer and FireFox.

You'll notice that the left margin is -390px. The pop-up window acts as it should on the checkout page, though.

I had to change the Pop-up mode to mootools.