Version: (using KDE 4.2.0) OS: Linux Installed from: Unlisted Binary Package Slightly obscure bug, but pretty severe: click the left top button in the window decorator of an open app, choose 'advanced', choose 'special application settings' (I think, I use Danish kde), go to the 'settings' tab and choose 'shortcut' and map it to <whatever shortcut> and set it to 'remember'. Upon closing this app, X will freeze. Repeating the process doesn't show any trace of kwin having remembered this setting, so unsetting it isn't possible via gui. The app in question will from then on freeze X whenever it is being closed. tested with multiple kde apps.
*** This bug has been marked as a duplicate of bug 184142 ***