Membership – Can't complete payment – won't get past subscription page

Hi,

I have installed the Membership plugin to my site, it all seems to be working well apart from When I try to sign up to a product, the pop-up box appears with my payment options, I click on subscribe and nothing happens (it takes me to a page that shows the same details that are in the pop-up box).

Furthermore, if I select that registration should be a page not a pop-up, when I click subscribe, it just takes me back to the home page. This is a pretty serious problem – can someone help me out and take a look?

website is Here – Obviously click on register on the menu

Thanks,

Sam