Asking problem of projector

[Seto1]

I’m trying to create a real-time terrain editing as the editor does.
And I find the projector confused. I’m using the same way as the Editor. Use wrapmode as repeat. And it returns me the situation like this.
http://www.shineinthebox.com/WebPlayer/WebPlayer002/
The projector project to the terrain filled with textures.
And I try to modify the wrapmode to clamp. It returns this.
http://www.shineinthebox.com/WebPlayer/WebPlayer/
Yet, if you use the third brush and you will see the problem.
Can anyone help me?

[Seto1]

Here’s screenshots.
002 is the wrap mode in repeat. 001 is the wrap mode in clamp.

[Seto1]

No one knows why?