For some reason when I select "Lock Session" in KDE nothing happens and if I try to Configure KDesktop and click on Screen Saver, the window crashes and if I try to select another desktop, its a black screen and I have to reboot my system as system/KDE locks up. Actually its a strange phenomena, applications which are already running keep running but the desktops disappear and trying to get a context menu with right-mouse button is inefective and a reboot is required for full functionality. I think this occurred after a crash and e2fsck does not fix it. Any Idea how I can fix this problem please?