Depth fighting problem!

Hi
First i must say Thank for Caelum , its Excellent !
Im using Ogre Source 1.6 final+Caelum-0.3.0
Caelum Demo(without any change here) have Depth Fighting problem when i run it in DirectX mode, i mean that terrain surface have Depth Fighting problem with a black plane! i don't know what is it.
In OpenGL i have't the problem.

My system configuration :
CPU:Intel Quad-Core QR6800
GPU:NVidia 8800 GTX
RAM:4GB
OS:Vista X64
Note: I have last version of NVidia driver for my graphic cards.

Thanks for any help
H.Ahmadi

The issue was due to demo materials mixing fixed function and shader passes. It no longer happens in trunk (it was fixed a long time ago).