I wish I could just switch to another virtual console, but it is impossible! There is no keyboard response, except ctrl-alt-backspace. Nothing else produces any result. The black screen with the mouse pointer, which is fully movable, just hangs. There is no going to any virtual console until I have killed off X, and then I am taken to the command line login prompt. No gdm. I will try ps next time it happens, but in order to execute ps, I will have to kill the X session. Would not any "kde process hanging around as a zombie" also be gone then? I will see what happens. This last logout just worked, to my astonishment. I am about to log out again, so I will see what happens.