You may have a problem trying to login to change information in your membership section in PlayOnline. This is because you purchased a FFXI account with a different FFXI version (example you purchased an Europe version when you are currently accessing an USA version). In order to fix this, you will need to download a different version which can be run as a second application on your desktop (it will not overwrite your US version).
DOWNLOAD USA VERSION
DOWNLOAD EUROPE VERSION
This should solve all your problems with Final Fantasy XI. If you run into more problems, feel free to contact our support via email for additional assistance.