Shopping Cart not working

When I go to the demo website, and I add one of the test products (add to cart) then the browser does a POST , which updates the shopping cart.
After installing the hot installation on my own server and configuring the virtual mart installation file, I try to add a product, the browser is unresponsive and does not do a POST and no item is added to the shopping cart. I attached screen shots what your website looks like when I try to add an item to the shopping cart and the same thing for my own browser.

I just tried to add products to the cart on your site www.markusskriver.com/store/outwear and it worked fine.

It does not work for us! We tried it on different computers with firefox , safari and google chrome, the cart is not updated and still stays empty... Can you give more information , please? Thank you!

Please see attached.