These are bugs that I'm aware of but haven't been able to fix.
You will have to use the TAB key or mouse to change the focus.
This is a known Java bug. See: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6449451
If you are using KDE, don't click on the close button for any dialog box that has the shade setting on otherwise the dialog box won't go away until you quit or killed the application.
I think this is a Java bug. See http://bugs.kde.org/show_bug.cgi?id=135146
Sometimes the dialog boxes won't accept keyboard input (including mnemonics) even though they have the focus
Switching the focus to another application and then back again fixes it. I can't consistently reproduce this problem.
This is caused when the text field used in constructing a text area is located slightly off the actual position of the text area. I think this is because the text field uses integer dimensions whereas the text area is painted using floating point dimensions. This problem is therefore most likely due to rounding errors.
I think this may be related to http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6726691. It doesn't occur with Java version 1.5.0.