In case someone with the same or similar problem visits this thread, thought I should note that I was able to display Japanese in the search textfield when I changed themes.
Windows theme & Default theme --> displays Japanese
Pro theme & Black theme --> doesn't display Japanese

Experience may differ depending on your OS setup and LimeWire version. Still not sure how to use Japanese user interface. The international version's setup only had options for European languages even though Japanese translation is reported to be 100% complete at the time this page was last updated.

Would be nice if the international ver. supported all fonts no matter what one's OS setup was. Mozilla seems to be able to do this.