Hi Fioli -
Sorry about the problem. We know what the problem is, we just aren't sure how to resolve it yet. But, I can tell you how to avoid it.
The forum script makes a mistake sometimes when there are no spaces for a long time, as is natural for Japanese text. It expects spaces like with English. So, if you put a space every now and then, it will work fine, but if you leave no spaces at all for a full line, then the problem will sometimes happen. You can do a test on this thread to see what I mean.
We are working on it, I promise!
As far as the problem you were having previously (at the start of the thread) - I think it has been resolved, right? We converted both English and Japanese forum interface into UTF-8, so everything should work ok with the encoding now, I think.
Thanks again for the feedback and I will post an update once we resolve the spacing issue.