touch is not working

in my game i have 4 scene ,one of them is may mainmenu i have some keys in this scene so i write a code that is=
if (Input.touchCount > 0)
{
var ray = Camera.main.ScreenPointToRay (Input.GetTouch(0).position);
var hit : RaycastHit;
if (Physics.Raycast (ray, hit))
{

           Debug.Log(" You just hit " + hit.collider.gameObject.name);

    if(hit.collider.tag == "newGame")
    {
     Application.LoadLevel(2);
    } 
	
    if(hit.collider.tag == "guide")
    {
     Application.LoadLevel(5);
    } 
    if(hit.collider.tag == "aboutme")
    {
     Application.LoadLevel(4);
    } 
   }
  }

to use touche and it work very well in my mainMenu but when i write this code for my another scene it not working and always it get Eror that is =Objetc reference not set to an instance of an object)
and if i had some mistakes in may question its for that i cant write english well
please help me…i realy need this

Make sure that your camera has “MainCamera” tag on it. That’s the only thing that comes to mind, touch should work :frowning: