FULL PRODUCT VERSION :
java version "1.6.0_10-beta"
Java(TM) SE Runtime Environment (build 1.6.0_10-beta-b25)
Java HotSpot(TM) Client VM (build 11.0-b12, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
With Nimbus L&F (as of 6u10 build 25) it is not possible to use a MouseListener on the BasicSplitPaneDivider of a JSplitPane, the event methods never get called.
With Windows and Metal look and feels this works as expected.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
(Compile and run the source code provided)

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
mouseClicked() should get called and print "mouseClicked" when clicking (but not moving) the divider.
ACTUAL -
mouseClicked() never gets called, the same is true for other MouseEvents.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package test;

import java.awt.event.*;
import javax.swing.*;
import javax.swing.plaf.basic.*;

public class DividerClickTest
{
    public static void main(String[] args) throws Exception
    {
        UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");

        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, new JPanel(), new JPanel());

        BasicSplitPaneDivider divider = ((BasicSplitPaneUI) splitPane.getUI()).getDivider();
        divider.addMouseListener(new MouseAdapter()
        {
            public void mouseClicked(MouseEvent e)
            {
                System.out.println("mouseClicked");
            }
        });

        frame.add(splitPane);
        frame.setSize(400, 200);
        frame.validate();
        frame.setVisible(true);
    }
}
---------- END SOURCE ----------

Release Regression From : 6u6
The above release value was the last known release where this
bug was not reproducible. Since then there has been a regression.