Comment 9 for bug 182288

Ivan Baykov: Your simple solution worked perfectly for me.

I played around with visualisation settings in KDE4 and, when logging back in, I was greeted with a black screen and a white mouse cursor. Everything functioned as normal, but I just couldn't see anything. Changing the compositing setting and restarting the X server fixed this.

I'm not certain whether this is the same problem Andrew Manson (original poster) was having, but it did seem very similar to the symptoms of other commenters here.

I haven't tried playing around with effects again, and I probably won't for a while. I'm using an ATI card in an ASUS laptop and I understand they're not the most reliable cards for KDE . . . yet.