Instantiated object collider not working?!

Hello,

I'm instantiating an object like this

Code (csharp):

1. var cube : GameObject;
2. Instantiate(cube, Vector3.right, transform.rotation);

Part of the cube GameObject include a rigidbody and a box collider. Why the original cube collider works when falling on a plane while the instantiated one suddenly falls off the plane as instantiated? I've tried to lower the plane, but I have the same problem.

One cube falls on the plane correctly, the other pass on it as it has no collider.

 

Are you using a prefab to instantiate it, or are you just cloning the object? I'd recommend using a prefab if you're not changing parts of the gameobject dynamically (besides its position).