Did you get the verification email with a link to validate your registration? If you did and you clicked on the link from inside the email, copy&paste that link into your browser instead. The link is sometimes two lines, and clicking on it only copies one line into the address bar. By copying and pasting, you'll get the whole thing without leaving the verification code at the end.
Also, keep in mind that a forum account and a game account are not the same thing. If you've made that mistake, you can register for a game account
here.
