Is there any reason why the View->Advanced->Visibilities Clip slide bar and Depth Cue slide bar would be be disabled? It worked at one time. (v. 2000i).
The clip function needs an accelerated graphics card and it needs to be on. If you are using win_32_gdi as your graphics setting in config.pro then you can't clip. The same is true for UNIX if you are using x-windows.