I'm running Kubuntu 11.10. Once I log out of my system, the screen goes blank, though I can still see the mouse pointer and when I move it to where text fields for username and password should be, it does change its icon. Going on a whim I enter my password and I do appear to get logged in, only the black screen continues to stare at me after which I restart kdm/computer. Any idea about what is wrong or how I could debug this?