Same here. I have already registered 3.0 trial and 3.0 permanent. Now when I try to do it with 4.0 I get same message - already registered.
And something more. When I try to do this with 3.0 permanent license key I get e-mail with notification that me or somebody else try to registered key again, now I didn't get it (with 4.0). Maybe somebody stole ours keys?
I have more problem with it - I can't activate my 4.0 but I send support ticket and now I'm waiting for response.
R.