Steps to Reproduce:

1) Launch SwingSet2 demo.
2) Click the "JFileChooser Demo" button.
3) In the JFileChooser Demo, click "Show Custom JFileChooser" button.
4) Notice that the "Custom JFileChooser" Window has the Default L&F.
5) Now close the "Custom JFileChooser" window and chnage the L&F using the "Look & Feel" Menu of SwingSet2 Demo.
6) Now again launch the "Custom JFileChooser" window. Notice that this window still has the previous Default L&F i.e its L&F doen't change to the one you recently selected from the "Look & Feel" menu.

Whereas the L&F of "Preview JFileChooser" and "Plain JFileChooser" does change to the new L&F selected from the "Look & Feel" menu.

This occurs on all platforms.

%java -version
java version "1.4.0-beta_refresh"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta_refresh-b67)
Java HotSpot(TM) Client VM (build 1.4.0-beta_refresh-b67, mixed mode)