I have the same problem, I was testing shadow and dynamic light, result;

Shot at 2007-09-10
Verry strange shadow, because the light is directly above and in the center of the box. So I expected a shadow on the floor around the box and not only on the left.
There is no sun, only a little ambiant lighting (10,10,10).
And the light is also seen inside and in front of the box. (It penetrate through the walls)