Compile and run the following codes under jdk1.3.1, you will find that the new created frame will move automatically, but under jdk1.2 and jdk1.4, the codes work well.

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

public class Test {
    public Test() {
        JFrame f = new JFrame("Test JFrame");
JPanel p = new JPanel(new FlowLayout());
JButton btn = new JButton("New Frame");
btn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent evt) {
JFrame newFrame = new JFrame("popup frame");
JPanel pp = new JPanel();
pp.setPreferredSize(new Dimension(300, 400));
newFrame.setContentPane(pp);
newFrame.pack();
newFrame.setVisible(true);
}
});
p.add(btn);
f.setContentPane(p);
f.pack();
f.setVisible(true);
    }

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

following is the java version info:

java version "1.3.1"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.1-b24)
Java HotSpot(TM) Client VM (build 1.3.1-b24, mixed mode)