Re: KDE Desktop is frozen during cube rotation with direct rendering
I managed to get the cube to crash, but only when I set "OpenGL mode" to "Fallback" in the advanced tab. Since this option wasn't specifically called out in your problem description, can you clarify what OpenGL mode you're using? (The default was "Texture From Pixmap".) The crash I saw could be related, but it's hard to be sure...
Can you attach a debugger to kwin and post the backtrace when it crashes? It would be interesting to see if the call stack is similar in your case. (I'm assuming that kwin is crashing in your case too, but if it's a different bug, then that might not be the case...)