Click to move disregards collision?

Alright so if i use the following code`

// Click To Move script
// Moves the object towards the mouse position on left mouse click
 
var smooth:int; // Determines how quickly object moves towards position
 
private var targetPosition:Vector3;
 
function Update () {
	if(Input.GetKeyDown(KeyCode.Mouse0))
	{
		var playerPlane = new Plane(Vector3.up, transform.position);
		var ray = Camera.main.ScreenPointToRay (Input.mousePosition);
		var hitdist = 0.0;
 
		if (playerPlane.Raycast (ray, hitdist)) {
			var targetPoint = ray.GetPoint(hitdist);
			targetPosition = ray.GetPoint(hitdist);
			var targetRotation = Quaternion.LookRotation(targetPoint - transform.position);
			transform.rotation = targetRotation;
		}
	}
 
	transform.position = Vector3.Lerp (transform.position, targetPosition, Time.deltaTime * smooth);
}

then my player that was behaving so nicely before just falls through the world. im almost dead positive that it has something to do with this line

transform.position = Vector3.Lerp (transform.position, targetPosition, Time.deltaTime * smooth);

again, before i implemented this code the player was not falling through the world, and now it is.

resolved my own issue, turns out the player was a child of something that was making it act really funky in relation to the box collider - still not very fluent with these sorts of hierarchy issues >.<