colliders dont work in my project

My main character(exported form 3dmax) doesnt collide with anything around him!!... Ive tried making a new scene with some obstacles and it works perfectly, but soon as I bring it back to my scene ( where I have a terrain and some props made in 3dmax as well) it doesnt work at all, he just goes through the obstacles and doesnt collide with anything! I need some help!... it is very weird, because im doing exactly the same thing with the other scene is there a chance theres something to do with the .fbx?... Im using a character controller and this script:

var speed : float = 10.0; var jumpSpeed : float = 8.0; var gravity : float = 20.0;

private var moveDirection : Vector3 = Vector3.zero;

function Update() { var controller : CharacterController = GetComponent(CharacterController); if (controller.isGrounded) { // We are grounded, so recalculate // move direction directly from axes moveDirection = Vector3(Input.GetAxis("Horizontal"), 0, Input.GetAxis("Vertical")); moveDirection = transform.TransformDirection(moveDirection); moveDirection *= speed;

    if (Input.GetButton ("Jump")) {
        moveDirection.y = jumpSpeed;
    }
}

// Apply gravity
moveDirection.y -= gravity * Time.deltaTime;

// Move the controller
controller.Move(moveDirection * Time.deltaTime);

}

Colliders won't stop objects from moving through eachother. They exist to detect collision. If you want collision response you need to have a RigidBody attached as well.