Gamespy powered by gamespy is still in existance and no that means the cd key that you have registered with the game is bound to another account and not the account you are trying to input.
Go to
http://www.poweredbygamespy.com/ and on upper right make sure you can login to your account fine and think of any other accounts you may have used, also make sure nickname you are using is the default nickname of your gamespy account.