Even with the new file I can't reproduce the effect here anymore. I've tried all machines that we have. First I thought that's because the engine I use is slightly different, but I also can't reproduce it with the 7.07 release version. nVidia couldn't reproduce it either.

I know that I've seen the effect, but it seems to be mysteriously disappeared.

Can everyone whose PC is suffering from this effect post his 3D hardware type and driver version here?