11.2RC1, M8 but probably related to KDE 4.3 (and possible 4.x)

Personal settings > Windows > Window Decoration (default tab)

Although the option Close windows by double clicking the menu button is checked, double clicking the menu button (top left icon on window title bar) doesn't close the window, but toggles the menu. In 10.3/KDE3.5.x it works as expected. Any ideas?

Thanks.