I just installed 11.0 (upgrade from 10.3), and was using KDE 4 for the first time. I was fiddling around with the new eye candy for desktop effects, etc., enabled a particular effect, and got hosed. The windows went blank and dimmed for a few seconds, then my screen went to all black, except for the mouse cursor, which I can move around freely. Ctrl-Alt-Bkspc kills and restarts X, but I still just end up with the black screen and mouse cursor after it restarts. I can only assume it has something to do with the effect that I tried to enable.
I can log in to KDE 3, so is there a way to revert the settings back to the defaults from there? Then, I’ll just remember not to enable that effect again.