I want to upgrade to pro, but the payment process seems broken.

I want to upgrade back to my pro account, but I can't ever get through the payment process. I want to pay with paypal. I get to the screen that says "How would you like to pay for this service?" and select the paypal radio button then hit the "Continue" button. It turns gray, and nothing happens. Any clue about what's going on? I'm using the Safari browser.