I have a frame, which contains textarea , menus & a button. Clicking on the button , removes menus from menubar & add them to popupmenu. For each click menus are removed & added back between menubar & popup menu.
Note:- When the menuitems in the menu is increased to the screen size. In windows we can navigate through the other menuitem by clicking the arrow button which is seen in the last & first menuitem. This is the known issue.

Clicking on the disabled down arrow menuitem(after reaching the last menuitem. I have attached the screen shot(clickhere.PNG)) for some 4 to 5 times & clicking any menu items or some where on the screen, results in moving the vertical scrollbar tumb towards the down arrow of the textarea.

Step to reproduce:-
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1) Run the attached program.
2) Click on the "Click Me" button. Observe that menus in the menubar are removed.
3) Click on the "Click Me" button several times. so that "Dummy" menuitem gets added to the "File Menu" in the popup menu & arrow menuitem are added to the "File" menu as in the attached screen shot. For each click menus are removed & added back between menubar & popup menu.
4) Type some character into the textara. say 15 to 20 lines.
5) Select some characters from the first line of the textarea.
6) Right click on the selected text. Observe that popup menu is visible. Move the mouse on the "File" menu & click 5 to 6 times on the down arrow menuitem ( as shown in the attached screen image). Observe that vertical scrollbar tumb is moved towards down arrow of the textarea. If you see the same then the bug is reproduce.

I tested this in windows xp . This is reproducable from jdk1.4.2 to jdk7.0 b09