problem creating static class that does not need to be instantiated

[sirzooass]

I'm trying to set up a static class that does not need to be instantiated but I keep getting smacked with the error:

Spring.as, Line 26 1119: Access of possibly undefined property onEnterFrame through a reference with static type Class.

If I have an object I wish to spring I just call
Spring.springToMouse(movieClipToSpring);

I'm thinking the fix must be quite simple but can't nail it. Any help would be much appreciated.

package
{
	import flash.display.*;	
	import flash.events.Event;
	
	public class Spring extends MovieClip
	{
		private static var springController:MovieClip = new MovieClip();
		private static var springObj:Object;
		private static var spring:Number = 0.1;
		private var targetX:Number = 0;
		private var targetY:Number = 0;
		private var vx:Number = 0;
		private var vy:Number = 0;
		private static var friction:Number = 0.95;
		
		public function Spring()
		{
			
		}
		
		public static function springToMouse(obj:DisplayObject):void
		{
			springObj = obj;
			springController.addEventListener(Event.ENTER_FRAME, Spring.onEnterFrame);
		}
		
		public static function springStop():void
		{
			springController.removeEventListener(Event.ENTER_FRAME, Spring.onEnterFrame);
		}
		
		public function onEnterFrame(event:Event):void
		{
			var dx:Number = mouseX - springObj.x;
			var dy:Number = mouseY - springObj.y;
			var ax:Number = dx * spring;
			var ay:Number = dy * spring;
			vx += ax;
			vy += ay;
			vx *= friction;
			vy *= friction;
			springObj.x += vx;
			springObj.y += vy;
		}
	}
}

I do realize I can alternately apply the sprining like so
var objToSpring:Spring = new Spring(this);
objToSpring.springToMouse();
and use the code below, but I'd still like to know how to get it working, plus I'm not sure which way is better performance wise if either.

package
{
	import flash.display.*;	
	import flash.events.Event;
	
	public class Spring extends MovieClip
	{
		
		private static var springObj:Object;
		private static var spring:Number = 0.1;
		private var targetX:Number = 0;
		private var targetY:Number = 0;
		private var vx:Number = 0;
		private var vy:Number = 0;
		private static var friction:Number = 0.95;
		
		public function Spring(obj:DisplayObject)
		{
			springObj = obj;
		}
		
		public function springToMouse():void
		{
			this.addEventListener(Event.ENTER_FRAME, onEnterFrame);
		}
				
		public function springStop():void
		{
			this.removeEventListener(Event.ENTER_FRAME, onEnterFrame);
		}
		
		public function onEnterFrame(event:Event):void
		{
			var dx:Number = mouseX - springObj.x;
			var dy:Number = mouseY - springObj.y;
			var ax:Number = dx * spring;
			var ay:Number = dy * spring;
			vx += ax;
			vy += ay;
			vx *= friction;
			vy *= friction;
			springObj.x += vx;
			springObj.y += vy;
		}
	}
}

Also, perhaps there is some other piece of code going awry that I can't locate, but the the enterFrame loop eventually gets removed, almost as if the garbage collector snagged it.