Bug found in billing details region dropdown[checkout page]

Hi,
My wp ecommerce plugin version is 3.8.13.1.In the general tab I have choosen base country and region as USA and New Jersy respectively.There i noticed a bug in the checkout page.When i fill the billing details and shipping details manually then every thing is fine.The problem occurred when i tick the check box(“Same as billing address”).Then my billing details(country and region only) revert back to base country and regions though i changed those, in the same time shipping address is fine.So what is the problem.please find a quick solution

http://wordpress.org/plugins/wp-e-commerce/