Rotating camera around object up/down problem

Hey everyone! Ive been into unity3d for a few days now, ive browsed through several Q&A posts and havent found solution to this yet. What im trying to do is make the main camera orbit around player when pressing WASD keys. A and D are working perfectly fine, but W and S are having problems, the camera starts to rotate very weirdly when pressing them. Its hard to describe the movement that camera makes, but i think you can find the issue in my code.

 #pragma strict
 
 var Target : Transform;
 var CameraSpeed = 0.1;
 var DistanceToPlayer :  float;
 var xRot : float;
 var MaxX = 55;
 var MinX = 5;
 
 private var point;
 
 function Start () {
 }
 
 function Update () {
     xRot = transform.eulerAngles.x;
     point = Target.position;
     if(Input.GetKey(KeyCode.A)){
         transform.RotateAround(point,new Vector3(0f,1f,0f), CameraSpeed);
         transform.LookAt(Target);
     }
     if(Input.GetKey(KeyCode.D)){
         transform.RotateAround(point,new Vector3(0f,-1f,0f), CameraSpeed); 
         transform.LookAt(Target);
     }
     if(Input.GetKey(KeyCode.W) && xRot < MaxX){
         transform.RotateAround(point,new Vector3(1f,0f,0f), CameraSpeed);
         transform.LookAt(Target);
     }
     if(Input.GetKey(KeyCode.S) && xRot > MinX){
         transform.RotateAround(point,new Vector3(-1f,0f,0f), CameraSpeed); 
         transform.LookAt(Target);
         
     }
 }