Error is in your code which you didn't publish.
Multiple Listeners do work fine.

import java.awt.FlowLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JButton;
import javax.swing.JFrame;

public class GUI {
    public static void main(String[] args) {
        new GUI();
    }
    public GUI(){
        JFrame frame=new JFrame();
        frame.setLayout(new FlowLayout());
        frame.setSize(500, 400);
        JButton button=new JButton("Click me");
       frame.add(button);
       button.addMouseListener(new MListener());
       button.addMouseListener(new MListener());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
    class MListener extends MouseAdapter{
        public void mouseReleased(MouseEvent e) {
            System.out.println(this+" "+e);
        }
    }
}

Alex.
http://www.myjavaserver.com/~alexfromohio/