Mecanim Tutorial Model Falls Through Terrain

I am doing the Mecanim animation tutorial and for some reason, my characters falls partially through terrain. I did not alter anything outside of what the tutorial instructed me, yet the robot still falls through. Any ideas why? I am very new to Unity and have no clue.

This tutorial: Unity 4.0 - Mecanim Animation Tutorial - YouTube

The problem you mentioned is because of the height in which the animation for the character took place.

Because unlike the character itself, the animation does not follow any physics collision. Thus, if you can repeat it near, say a wall, you may notice that the character actually went inside a wall until the animation ends and the character’s collision box comes into effect.

As for a solution, unfortunately I am currently too unskilled to answer that. However, as to what the problem is, I believe this would be it since I too took part in the tutorial.