Hi,
it is a small bug/mistake and can be solved easily.
Please open this PHP file:
yourdomain.com/templats/<yourjoomlatemplate>/html/com_virtuemart/cart/default_prices.php
Look for these lines:
<a class="details" rel="facebox" rev="iframe|480|560" href="<?php echo JRoute::_('index.php?option=com_virtuemart&view=user&task=editaddresscart&addrtype=BT&tmpl=component&flexible=edit',$this->useXHTML,$this->useSSL) ?>">
<?php echo JText::_('COM_VIRTUEMART_USER_FORM_EDIT_BILLTO_LBL'); ?>
</a>
You will see this line in 2 different places. Simply delete the 1st one, it should be around: 172th - 177th