FULL PRODUCT VERSION :
Java(TM) SE Runtime Environment (build 1.6.0-b105)

ADDITIONAL OS VERSION INFORMATION :
Ubuntu 7.04(Linux 2.6.20-16-lowlatency)

A DESCRIPTION OF THE PROBLEM :
A regression of http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4893567.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile the source code below and see the background color of the second JTextField is not red.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The background color of the second JTextField should be red.
ACTUAL -
The background color of the second JTextField should is white.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.*;
import javax.swing.*;

class Test extends JFrame {
    Test() {
        try {
            UIManager.setLookAndFeel(
                    "com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
        } catch (Exception e) {
            e.printStackTrace();
        }
        JTextField textField1, textField2;

        getContentPane().setLayout(new GridLayout(0, 1));
        getContentPane().setPreferredSize(new Dimension(200, 100));
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        textField1 = new JTextField("WHITE BACKGROUND");
        textField1.setBackground(Color.WHITE);
        getContentPane().add(textField1);

        textField2 = new JTextField("RED BACKGROUND");
        textField2.setBackground(Color.RED);
        getContentPane().add(textField2);

        pack();
        setVisible(true);
    }

    public static void main(String[] args) {
        new Test();
    }
}
---------- END SOURCE ----------

Release Regression From : 5.0
The above release value was the last known release where this 
bug was not reproducible. Since then there has been a regression.