It happens when you update the system and probably also when you install new programs that are added to the menus.
My panels are placed at the bottom of the screen, yes. And I'm running updated Dapper. -- Menu scrolling is unpredictable https://launchpad.net/bugs/46061 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
