Sometime between builds 32 and 35 of jdk 1.5, selection in JFileChoosers was broken.  I will attach a demo app.

The problem manifests when file selection mode is DIRECTORIES_ONLY and multi selection enabled is true.  We use this mode to enable users to mount filesystems to add them to their classpath in NetBeans/Sun Java Studio.

Try the attached demo application (check or uncheck the checkbox to turn on/off the problem flags).

Note the behavior is not specific to the windows XP UI delegate - the same behavior manifests when using MetalLookAndFeel.

Specific problem:  With these flags, it becomes impossible to change the selection in the folder combo box at the top of the JFileChooser - you may select, but when the popup closes, the selected item is not changed, so it is impossible to navigate between directories.

See also 
http://www.netbeans.org/issues/show_bug.cgi?id=39374