Start Notepad demo in jdk then follow below steps.
% java -jar Notepad.jar
1. ctrl + space. Native input method enabled.
2. hit a, i, u, and e. They are not yet committed at this point.
3. Click save button.
4. Filechooser opens. a, i, u, and e are committed.
5. Close Filechooser.
6. Input something, for example, a.
It should display 1 hiragana "a" but displays it double. And hereafter, input has problem. Cannot commit.

This problem is visible in latest JDK 5.0, not in JDK 6 and later.
Reproducible using ja locale. When ja_JP.UTF-8 locale is used, native input method is disabled when closed Filechooser and this problem is not reproducible.