I have always had lighting problems with blender (GLSL), whenever I add a lamp, it goes through all faces, so a lamp’s light on one side of the map would show up on the other side. The only light I found that didn’t pass through faces was the spotlight (doesn’t light in all directions, so doesn’t help). I also lowered the distance of the lamp, but that didn’t help. I’ve seen some really good lighting in most BGE demos. how is this achieved?
Here is a video of the problem: