Black terrain patches

[11956-screen+shot+2013-06-13+at+8.58.58+pm.png|11956]

Hi, it is quite an obvious thing. Not sure why I even did a screenshot. I hope its clear.

Ok, I have a problem. When I create a new scene and create a new terrain, no matter what I do (raise terrain, etc), the thing comes out as black patches. The white portion is the new flat terrain with a directional light shining on it.

I try to do a search on similar problem here but the search in Unity3D forum and answer timed out.

Please advise. Thanks!

Try increasing the bias on you main light source.