FULL PRODUCT VERSION :
JDK 7u9

ADDITIONAL OS VERSION INFORMATION :
Apple Mac OS X 10.7 (Intel) (64-bit)

A DESCRIPTION OF THE PROBLEM :
An immediate call to JComboBox.showPopup() after JComboBox.hidePopup() does not lead to showing of a popup menu in JDK 7 on OS X, instead of this the popup menu just flashes. However the popup menu is always shown in JDK 6.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Compile and run the attached source code.
2. Click into any place of a displayed frame.

REPRODUCIBILITY :
The bug is reproduced always.

---------- BEGIN SOURCE ---------- 
import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.event.*;

public class TestWTDComboBox {
    static JComboBox kb = null;
    static boolean dataPopulated = false;
    static AWTEvent event = null;
    static JFrame frame;

    public static void main(String[] args) {
        frame = new JFrame("Creating a JComboBox Component");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);

        JPanel panel = new JPanel();
        String anArray[] = {"BCA", "MCA", "PPC", "CIC"};
        kb = new JComboBox(anArray) {
            @Override
            public void showPopup() {
                if (!dataPopulated) {
                    frame.dispatchEvent(event);
                }
                super.showPopup();
            }
        };
        kb.addPopupMenuListener(new PopupMenuListener() {
            @Override
            public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
                System.out.println("hello");
            }

            @Override
            public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
                kb.setPopupVisible(false);
            }

            @Override
            public void popupMenuCanceled(PopupMenuEvent e) {}
        });
        panel.add(kb);
        frame.add(panel);
        frame.addMouseListener(new MouseListener() {
            @Override
            public void mouseClicked(MouseEvent e) {
                System.out.println("hello111");
                event = e;
                test();
            }

            @Override
            public void mousePressed(MouseEvent e) {
                System.out.println("hello111");
                event = e;
                test();
            }

            @Override
            public void mouseReleased(MouseEvent e) {
                System.out.println("hello111");
            }

            @Override
            public void mouseEntered(MouseEvent e) {
                System.out.println("hello111");
            }

            @Override
            public void mouseExited(MouseEvent e) {
                System.out.println("hello111");
            }
        });

        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                frame.setVisible(true);
            }
        });
    }

    public static void test() {
        Object prevSel = kb.getSelectedItem();
        boolean isDropDown = kb.isPopupVisible();
        kb.hidePopup();
        kb.removeAllItems();

        kb.addItem("none");
        kb.addItem("none1");
        kb.addItem("none2");
        kb.addItem("none3");
        dataPopulated = true;
        kb.setSelectedItem(prevSel);

        kb.showPopup();
        dataPopulated = false;
    }
}
---------- END SOURCE ----------