Raycast point to provive a target not working?

hello. I want to create away for an object to look at a 3d point in space, which my mouse hovers over. i've done this by projecting a raycast from my mouse to my 3d world, and using the '.point' api as the target Vector3 on the look at script. how come this ain't working?

i also want a graphic to be displayed off of the normals of the object my mouse hits, and i tried this with a particle emitter but it still doesn't work.

here's the code :

    static var previousHit : RaycastHit;
    private var previousColor : Color;
    private var bObjectSelected = false;
    var marker : GameObject;

    private var firstInit : boolean = true;

    function Update () 
    {
         var ray = Camera.main.ScreenPointToRay(Input.mousePosition);
         var hit : RaycastHit; 

         if(Physics.Raycast(ray,hit, Mathf.Infinity))
         {
             previousHit = hit;

             if(firstInit)
             {
                 Instantiate(marker, hit.point, Quaternion.identity);
                 firstInit = false;
             }

             if(hit.collider.gameObject.tag == "Selectable" && Input.GetButton("Mouse1"))
             {
                 previousColor = hit.collider.gameObject.renderer.material.color;
                 hit.collider.gameObject.renderer.material.color = Color.green;
                 bObjectSelected = true;
                 previousHit = hit;
                 print("Hit selectable");
             }

         }

    }

function LateUpdate()
{
    marker.transform.position = previousHit.point;
}

it works when first instantiating the marker, the marker spawns under the mouse, but when i move the mouse, the marker doesn't follow?

I found that out that, creating a Vector3 Variable, and assigning it to the PayCastHit.point every frame, worked.