Object odd light problem with mesh?

Hi.

I have a simple 3d game object model in the scene.

The surface looks like this in the scene: Image 1

When I now add the "MeshMerger" script to the object and start the game, I get this: Image 2

I really don't know why? Maybe there is a problem with the vertices after merging. The directional light then can't read these vertices?

The script can be found here: http://wiki.unity3d.com/index.php?title=MeshMerger