I have found that the easiest, most efficient way to check out on here is instead of using the PayPal button on the shopping cart page, to simply hit the button that says "Checkout". From there you still get an option to use PayPal and Google checkout. I prefer to stay on the site that way, while still getting the security of my PayPal payments.

Click on "Checkout". Still safe, but this time your order will actually go through!

Hope this helps!