Using Joomla 2.5.20, Multi language (only DK in VM), Beez20 copy template, Virtuemart 2.6.8, PHP Version 5.3.27 vm overrides.
Joomla site is live - danrider.dk - vm shop is only for registered shopper.
Updated our test site with 2.6.10 and turned on Beez20 template.
In check out - if you have a shipment address - the "Ship to same as bill to address" check box does not Work in IE 11 and Chrome - it Works in Firefox
updated to Joomla 2.5.24 and VM 2.5.10.
Virtuemart 2.5.10 works - re. above mentioned bug - if I DO NOT update my overrides which is the css and com_virtuemart/views
../cart/tmpl/default.php and default_pricelist.php,
../category/tmpl/default.php
../productdetails/tmpl/default.php and default_showprices.php
../user/tmpl/edit_vmshopper (emty in overrides)
mod_virtuemart_cart/tmpl/default.php
Updated our test site with Joomla 2.5.27 - VM 2.6.14 and turn on Beez20 template.
The "Ship to same as bill to address" check box is not working - can't mark it.
It only Works if I don't update my overrides as mentioned above. :-\
So it seems your overrides are broken. => use the original layout files and create new overrides by them.
... but it is with the Beez20 template ( original one ) turned on the check box do not Work.