Terrain Collider doesn't update/ how to create a new terrain Collider?

Hi,

I'm trying to create an modify terrains at runtime. So far I've donne this:

 //Time to create the first terrain based on the template that is in the scene
         tempTerr = Instantiate(TerrainTemplate, new Vector3(2000.0f, 0.0f, 2000.0f), new Quaternion(0.0f, 0.0f, 0.0f, 0.0f)) as Terrain;
         tempTerr.terrainData = Instantiate(TerrainTemplate.terrainData) as TerrainData;
         hMp = generateHeightmap(tempTerr.terrainData.GetHeights(0, 0, 513, 513), new Vector2(513.0f, 513.0f));    
         tempTerr.terrainData.SetHeights(0, 0, hMp);

At the moment the terrain is being created, and I can see the changes to the terrain (created by the generateHeightmap function). The Problem is that the player falls throught the terrain and stops at the bottom of the terrain(where the old terrain collider was(A flat terrainCollider)).

Bottom line: how do I update the terrain collider? The SetHeights function should do that but it doesn't. What can I do? A little/fast code example would be greatly appreciated.

Thanks for your time...

edit: I've already tried Flush() but nothing changed.