Thanks Ed for the explanation.
The IP Address should be exact.
The message that appears now does not refer to security violation; it explains exactly what is happening as follows:
Sorry, you cannot register in this Tourney, as another Player using the same IP Address (Internet Protocol Number or Address) has already registered in this Tourney.
Please note that this does not mean that you are cheating, as this might result for any of the following reasons:
When 2 Players are using the same Internet connection, or sharing a Network.
When Player 'ABC' logs out from the Internet, and then Player 'XYZ' logs in accidentally getting the same IP the Player 'ABC' was using when registering in the tourney.
When a certain ISP (Internet Service Provider) is assigning the same IP Address for so many users.
This system is applied to secure fairness to all Players. Sorry for any inconvenience caused.