Teegrins, Ickelz!

Unfortunately, Gamemasters can not usually do anything about reports from other players regarding issues another player is experiencing (it is not completely impossible for them to start an investigation depending on the case, though).

That being said, you should contact the Customer Service via the Support Centre/Center regarding any and all Account/Billing related matters.

Europe:
  • http://support.eu.square-enix.com/contacttop.php?id=455&la=2
Japan:
  • http://support.jp.square-enix.com/contacttop.php?id=11&la=0
North America:
  • http://support.na.square-enix.com/contacttop.php?id=20&la=1
Other:
  • http://www.square-enix.com/
As for my opinion on your issue, seeing that you are able to post here, I take it that you are able to log in the Square Enix Account Management System still.
If so, I would encourage you to change your password(s) where applicable.

Please do note, however, that if your Operating System has been infected by malicious software, such as a key-logger that records keystrokes and sends them out, it does not necessarily do much good to change account credentials whilst infected as the new passwords would likely be sent away as well.

This is why it is important to find out why it happened in the first place.
Since there is no such anti-virus/other software around that would be able to detect every possible harmful file, often the only sure way to get rid of such things is to do a complete re-install of the OS (in other words, deleting everything there is, and creating a fresh install). Back-up plan for important files is always good to have, no matter what the situation is.

If you use any kind of third-party applications with Final Fantasy XI, please do note that they are not supported at all (and actually violate the User Agreement/Terms of Service), and can easily cause issues with your game.
Based on your description, it might be that at least a re-install of the PlayOnline viewer and possibly Final Fantasy XI as well would be a good idea.

At least do the file-check before anything and see what it says.

You might also want to try to create a new member profile (Add Member) in case the old member data has been corrupt and thus shows you scrambled characters.
That said, are you certain it is indeed Japanese? I don't know for sure if the EU/US viewer even has the ability natively to display those characters (it probably does), but normally the client would allow selecting between English, German, and French languages only.

Considering you also mention the client crashing whenever you click something, this could be another indication of simply corrupt files, and could even mean that the hard-drive is going bad (might be worth running chkdsk (assuming you are using a Windows Operating System), and memtest86+ at least).


Just some thoughts~
Good luck!