The SE password may be correct, it's the one you are using to get into the forums and SE Account Management.

Usually, when this happens it's a mismatch between the saved POL password in either the client (POL settings in game) or at the server (saved with your account details in SE Account Management). Most likely it's becuase the console/PC playing FFXI will have the POL info saved and you are now only entering the SE credentials--people simply forget what their POL credentials are and wind up saving the wrong info (or in the wrong places).