Comment 14 for bug 182288

I can verify that this problem exists for nvidia cards and intrepid. I enabled compositing on two seperate systems with nvidia cards and after hitthing the apply button in some cases I was presented with a black screen and mouse cursor. On the second system, I don't recall enabling compositing effects but I must have tripped something because when I logged back into kde I received the black screen. I had to edit the kwinrc file and set [Compositing] Enabled=False to fix it.

Compiz desktop effects work fine in Gnome and compositing works fine in Xfce4.