Shadows not displaying correctly

[Daiyuki]

I have examined the screenshot more closely, but am not sure what the problem is. There are no shadows in that screenshot.

There is darkness, and it's the fading darkness that causes problems. As I move forward, I always see this retreating semi-green shadow-within-a-shadow. It's really hard to explain without being able to show you, so hopefully the video I made will illustrate what I mean:

http://www.youtube.com/watch?v=qe97rsU0fHY