SimpleMove Problem

void Update()
{
    CharacterController controller = transform.gameObject.GetComponent<CharacterController>();
    // Note nodeX, nodeZ are int's not floats
    float x = currentNode.nodeX;
    float z = currentNode.nodeZ;

    // Direction of target
    Vector3 direction = (new Vector3(x, 0, z)) - transform.position;
    // Ignore Vertical
    direction.y = 0;

    float speed = 4.5f;
    float distance = Vector3.Distance(new Vector3(x, 0, z), transform.position);

    // Do we actually need to move ?
    if ( distance > 0.0 )
    {
        // Find target direction
        Quaternion rotDir = Quaternion.LookRotation(direction);
        // Gradually rotate towards target
        float rotationSpeed = 5.0f;
        transform.rotation = Quaternion.Slerp(transform.rotation, rotDir, rotationSpeed*Time.deltaTime);
        controller.SimpleMove(transform.forward * speed);
    }
}