Blue poster Tyren made an announcement on the PTR forums this afternoon that those of us who have an account in the Wrath of the Lich King beta cannot participate in the 3.0.2 PTR. This is most unfortunate news for the numerous people in that situation.
If you have more than one account, your second account could probably work with the PTR (assuming it is not enrolled in the beta). I haven't been able to test this yet with my other accounts, but will update this post when I get the chance to.
Tyren does say that they are working to resolve the issue, and that it should be fixed early next week. In my opinion, it can't be resolved fast enough.