It was blocked because s/he hadn't registered it, and now s/he's had the registration link pointed out to him/her and accepted the answer, s/he's presumably registered his/her device.
Did you read the page before you posted it?
By the comments, that's not helping most people, apparently. The solution for them is to uninstall iOS5 beta by restoring the phone.
There's indeed a fix for this issue. Take a look at the trail of comments below. A lot of us had their phone and iPad suddenly blocked.
This smacks of silliness. People are using their development devices as their business and personal phones. This is called out in the developer agreement and every beta software agreement. Don't do that.