The problem can be reproduced with SwingSet2 Demo with 1.4.0_01 or 1.4.1-build10 on winNT

Start SwingSet2
Select JComboBox Demo Tab
Reduce the hight of the main window a bit shorter so that when we
select the presets menu, it pops up a menu that extends beyond the parent window.
Now minimize entire window.
And restore again to see the origianl menu and its content
*you notice the repaint problem at the location where there was a popup menu.
*Now try resizing the main window. The location on screen where the popup menu
 was posted remains unpainted and looks ugly.