IBus-based input methods don't work with a pop-up input dialog. Here's how to reproduce.

   1. Start the SwingSet2 demo
   2. Select the JOptionPain demo
   3. Click Show Input Dialog to pop up an input dialog
   4. Turn on an input method
   5. Input some text (the first time it works.)
   6. Closed the input dialog
   7. Click again Show Input Dialog
   8. Turn on an input method
   9. Type a key. Its corresponding character is displayed, but it disappears immediately.

What I observed are:

    * Reproducible with Anthy and Pinyig (probably with more IMs)
    * Reproducible only with IBus-based input methods
    * Reproducible with 6u23
    * The first time it works.

It's likely this is an IBus problem. But we should see if there's any workaround fix.
Found out that if I switch focus from the JTextField to JButton and back to JTextField, the problem goes away. Could be related to initial focus on showing a JDialog.