I am confused myself too, because the plugin works fine suddenly!
Well, I must summarize what I have done.
First, I found the plugin did not accept any Japanese so I reported it to your site, codewarrior.getpaidfrom.us.
Then, I myself searched and searched the way to display Japanese, and finally got at the fact that they were shown when variables changed to VARBAINARY in database.
Though Japanese were actually shown in chatting, there were no sounds and a warning message appeared when using Google Chrome.
I once again searched the way to fix this, and got at the truth that Flex/Ajax bridge (FABridge.js) was out-of-date, thus I replaced it as I mentioned in previous posts.
Now that the chat seemed to work fine, except that "Admin is offline" was always displayed, I had been using it until you replied to this topic.
Your suggestions were tested with the above-mentioned plugin, in which the database tables were changed to VARBINARY and FABridge.js was replaced with the newer one.
Manwhile, you appeared to update the plugin twice. However, I did not upgrade mine, because I was afraid it would be confusing if I upgraded the plugin while testing.
And your suggestions were all unsuccessful. So, I decided to try continuing the test with the latest version plugin of 1.3.6.
I did upgrad the plugin to 1.3.6 from old 1.3.4 or before, and once again returned the database table variables to default ones.
(Note that I always returned the variables to default values when I tested your suggestions.)
I tried your suggestion of the change in bp-chat/chat/lib/class/AJAXChatDataBase.php, but it showed nothing and applicable database tables become null (empty) as I reported.
So, I returned bp-chat/chat/lib/class/AJAXChatDataBase.php to original, and the thing happened. The chatting showed Japanese correctly.
Your upgrading the plugin to 1.3.5 with new Flex/Ajax bridge (FABridge.js) might have fixed the problem, which I was not sure as I have never tested.
Now that the plugin works properly, the only problem remains that "Admin is offline" still shows up even after changing "admin" to the correct username in CustomAJAXChat.php. Is this also happening only to Japanese users?