Recently active topics in Twitter tagged with signup

I'm trying to create a new Twitter account and keep getting the message "403 Forbidden: The server understood the request, but is refusing to fulfill it." when the browser tries to load https://twitter.com/account/create after I click "I accept. Create my account." on https://twitter.com/signup

As far as I can tell, I'm filling in the username, password, email, and captcha correctly (new username, email longer than 6 letters, tried reloading captcha to make sure it's fresh). My email is a gmail address...hopefully you're not blocking them (I assume I'd get an error message to that effect if you were).

edit: same results for third day in a row. I'm using Firefox 3.0.1 from a new static IP address, if that's useful.