iPhone Touch RayCastHit problem

Howdy, all.

I'm making a 3d hockey game for the iPhone, and I'm having a problem with my movement. I want it so that the active player moves to the place last touched. However, after a little while of playing, the z co-ordinate of the hit will wind up somewhere below the screen. I've made it output the screen positions of the touch, and that's not the problem. Any suggestions on how I should approach this problem? gameInfo.touchPoint is just a Vector3 I made for the GUI so that I can see the hit position in the GUI until this is solved. What's going on is that I'll touch a point that has a z of 5, and suddenly it'll think I'm touching at -13, then eventually bring itself back to 5. After this code is where I do my vector subtraction to get the character moving, but it seems like the problem is with the hit itself.

EDIT I added some script to trace out what I'm touching (gameInfo.touchObject = hit.transform.name; and then stuff to draw it through the GUI), and I'm still touching the ice even as this is happening. In another test, I rotated the camera so it was directly overhead, and this continued to happen.

Here's the code in question:

var count : int = iPhoneInput.touchCount; if( count == 1 && (state == ControlState.MovingCharacter) ) { var touch : iPhoneTouch = iPhoneInput.GetTouch(0);

 if (  touch.phase != iPhoneTouchPhase.Began )
 {
     if(touch.deltaPosition.magnitude > 70)
     {
         moving = false; 
         targetLocation = thisTransform.position;
     }
     else
     {
     var ray = cam.ScreenPointToRay( Vector3( touch.position.x, touch.position.y ) );
     gameInfo.touchPoint = touch.position;
     //Raycast to move the player
     var hit : RaycastHit;
     if( Physics.Raycast(ray, hit) )
     {
         //Check if the user has selected the Ice or another player, then allow movement to that location
         if((hit.transform.gameObject == iceGameObject) || (hit.transform.gameObject == puckGameObject)){
             var touchDist : float = (transform.position - hit.point).magnitude;
             if( touchDist > minimumDistanceToMove )
             {
                 targetLocation = hit.point;
                 gameInfo.hitPoint = targetLocation;
                                         gameInfo.touchObject = hit.transform.name;
                 moving = true;
             }

         }

         else{
             Debug.Log("hit: "+hit.transform.parent.name);
             moving = false;
         }
     }
     }

 }
 else
 {
     moving = false;
     //targetLocation = thisTransform.position;
 }

}