Problem with cart and checkout page

wp. 3.7
WC 2.0.18
Have disable all other plugins
When added to cart I can see in the browser this: http://perrasfoto.se/butik/artister/accept-8650/?added-to-cart=522
When clicking the button “add to cart” it takes me to the cart page, and I can see my product. But in the bottom left I see the text “cart is empty”. (Screenshot skogasfoto.se/kundbilder/felsokning-shoppen/cart-is-empty.jpg) If I now click on either the checkout or update button I be redirect to https://www.paypal.com/cgi-bin/webscr
This is driving me crazy. I have reinstalled both wp and woocommerce, twice.
I have a test site on another server with the exact same installation, theme and settings for the shop. That shop works perfectly fine. I’ve been talking to the host, and we have compared the server settings on anything that we can think of, but come up with nothing. The server this shop with this issue has a higher security, for example I cannot update inside the admin area without typing in the pass for ftp.

If I go to the page checkout myself, I can see my added product and the fields for filling in the name, address and so on.
Any idea what could be wrong?
The address for the site is http://www.perrasfoto.se

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