Http 500 error on submit in test mode

I am trying to use your stripe wordpress plugin, and I am very much willing to pay for it if I can get it working. When I try and submit a payment in test mode, it submits it and then reloads the page with a http 500 error. I know I don’t have the SSL set up yet, but the test version should work over normal http I thought? Do you know is there a fix to this? I tried setting up the page here: http://the-eatyard.com/checkout/

Thanks