Slerp Problem?: Enemy in Constant Rotation!

I am having a problem with an enemy in my game where the enemy is constantly rotating. I used Quaternion.Slerp to control rotation. Here is my script:

 @script RequireComponent(CharacterController)
    
 public var MarManRotateSpeed : float;  
 public var attacktarget : Transform;   
 private var selfplace : Transform;    
 // [...] 
    
 function Start()    
 {    
     selfplace = transform;   
 }
 function Update(){}
 
 function CoUpdate()    
 {   
     Debug.LogWarning("Success?");    
     while(true)    
     {
         // [...]    
         var target : Transform;    
         target = attacktarget;
         selfplace.rotation =  Quaternion.Slerp(selfplace.rotation,
                                 Quaternion.LookRotation(target.position-selfplace.postition),
                                 MarManRotateSpeed * Time.deltaTime); 
         // [...] 
     }    
 }

Am I using Slerp wrong? How do I fix it?