My cart just stopped working

I have been out of town and come home to find out that my cart no longer works… it will allow you to add products, but when you go to calculate shipping, it does not go any further!!! ???? i have been tying to figure it out for hours! Can someone please help me. to see what i am saying check out my site and try to purchase anything on there, it will not let you check out… its killing my business! http://www.klackdamas.com
all help is welcome thank you!

http://wordpress.org/plugins/woocommerce/