Component.setFocusable(boolean) is not working properly for every component. Everything is fine for AWt components but it's behaviour is not desirable with Swing, heavyweight & lightweight components,e.g. it's not working for JButton on any of the platforms ,be it solaris or windows or linux.
Run FocusTraversabilityBUG.java File(attachment) & if you see message "button should not be focusable" appearing on your screen than the bug is reproduced.