I'm also having problems registering for an iTunes Connect account (I want to publish to the iBookstore). I use my mac account sign it, go through all the sign up screens (including my Social Security Number) and fail at the last page when I try to submit the application.
I sent this problem to support and they asked for screenshots. I got the following reply:
Thank you for the screenshots and additional information provided in regards to the error you are encountering while attempting to apply for account.
We are currently reviewing your request. You will receive a response within two business days.
That was 12 days ago
I have sent follow up emails and tried to complete the online form again with no joy.
I'm using my itunes account (not used for anything else) and Safari 6.0.5 on a MacBook Pro running OS 10.7.5
Thanks!