JFileChooser.getSelectedFile may return subclass of java.io.File:
javax.swing.filechooser.FileSystemView$FileSystemRoot. During serialization
of this class there is fired exception NotSerializableException, that is
clearly a bug in JDK 1.4.0 JFileChooser implementation.
There may be other subclasses of java.io.File - all of them must be
serializable and preferably deserialize to an instance of java.io.File (or to a fully functional descendant of it).