Ahh sorry, figured you were using the object rather than an fx. So after dl'ing the cap and not being able to open the cap, because I dont have Drop Shadow 2 fx, which I've never herd of coincidentally, I would say that the fx is the issue. :P
I have used both dropshadow pixelshader and the dropshadow object and i must say the pixelshader is much better in my opinion. Maybe you can use it? Off course the effect had not very many options but I added offset and shadow opacity.