Cart button not linking to cart?

Bit odd, was working 2 weeks ago and I have done nothing to my WordPress since.

Now the cart button at the top right is not working, it links to the page that you are on.

Any ideas?

If you want to take a look at the site you can email me for the link jacktail[at]furstre.am
It is a private site so not going to openly link.

Thanks