When I run a 3D demo, I get a black screen. When I change the render option from D3D to OpenGL I see the 3D output for one frame only, and it goes back to black. Same when I change the render option from OpenGL to D3D I see the 3D output for one frame only, and it goes back to black. So how do I fix this? It doesn't matter what computer I run on, or which version. Help please!