Run the attached test. In the test I create a frame and an embedded frame, then put embedded frame into the frame. Inside the embedded frame there are several Swing components including JComboBox which behaves wrong: when I click on it, it is expanded (unfurled) and immediately collapsed back. If I expand the combo box with keyboard, it works correctly.

I tried to reproduce this bug using SwingSet2 applet from java.sun.com, but the applet works fine. I also tried to add JApplet into embedded frame (like it is done in browser) and place all the Swing components into it instead of embedded frame, but this doesn't help.

I suspect something is wrong with AWT grab, so I'm filing this bug against AWT, not Swing group. The test to reproduce the bug is attached.