The black-window-bug (or BWB) has plagued nvidia users with compiz for a long time now. Basically, it happens when the video card runs out of memory when using the GLX_EXT_texture_from_pixmap extension.
While you haven't said what video card you are using, I'm going to guess that it's an nvidia card and that you are either using compiz or KDEs built-in compositor, correct?
Adam
|