I can't see the light!

Now we're talking.

And guess what? Nothing was wrong. I tried running the code on my work's ATI x1300 and shadows correctly appeared.

I suppose my SIS 650 messes up with alpha testing. Disappointing.

And there's another useful information: OpenGL do not work through remote desktop. If you try to connect via terminal services, you'll see just flat shaded polygons. What I can't see is the logic behind this. Everything is computed on "server" side and I don't think there's a particular boost of network performances not shading and texturing. I'm pretty sure RDP protocol does a run length encoding optimization, but a spinning cube requires more updates on client's side than a static decaled teapot. Mysteries.