Position icon lags while panning

I have an overhead orthographic camera that I can pan and zoom on a map. My character's position is shown using a DrawTexture. The problem is that when I'm panning around the screen, the DrawTexture is a frame or so behind my movement, so it looks like it's jumping around. How can I keep the texture from lagging and jumping?

GUI code: var Controller1 : GameObject;

 var PositionIcon : Texture;
 
 
 function OnGUI () {
     var IconX : float;
     var IconY : float;
 
         IconX = camera.WorldToScreenPoint(Controller1.transform.position).x;
         IconY = camera.WorldToScreenPoint(Controller1.transform.position).y;
 
         
     GUI.DrawTexture(Rect(IconX-10,Screen.height-IconY-10,20,20),PositionIcon,ScaleMode.ScaleToFit, true);
     
     }</pre>

Important part of panning script: var fullMapCam : Camera;

 var panSpeed : float = zoomSize.025;

     if(Input.GetButton("Fire1")&&(Input.GetAxis("Mouse X")!=0||Input.GetAxis("Mouse Y")!=0)){
         fullMapCam.transform.position.x -= Input.GetAxis("Mouse X")panSpeed;
         fullMapCam.transform.position.z -= Input.GetAxis("Mouse Y")*panSpeed;
         Screen.lockCursor = true;
         }
     if(Input.GetButtonUp("Fire1")){
         Screen.lockCursor = false;
         }