[mickfallout]

    switch (timer.currentCount) {
	case 5:  this.Fon_2.scaleX = 1.1;
		this.Fon_2.scaleY = Fon_2.scaleX;
		break;
	case 10:  
		this.Fon_2.scaleX = 1.2;
		this.Fon_2.scaleY = Fon_2.scaleX;
		break;
	case 15:  
		this.Fon_2.scaleX = 1.3;
		this.Fon_2.scaleY = Fon_2.scaleX;
		break;
	case 20:
		this.Fon_2.scaleX = 1.4;
		this.Fon_2.scaleY = Fon_2.scaleX;
		break;
	case 25:
		this.Fon_2.scaleX = 1.5;
		this.Fon_2.scaleY = Fon_2.scaleX;
		break;
	case 30:
		timer.stop();
		timer.reset();
		break;
		}

уж если и юзать таймер, то зачем так сложно? не проще ли:

        if (timer.currentCount<30) {
		this.Fon_2.scaleX = 1+(0.1*timer.currentCount/5);
		this.Fon_2.scaleY = Fon_2.scaleX;
	}else{
		timer.stop();
		timer.reset();
	}

Добавлено через 7 минут
вариант с enterFrame:

package  {
 
	import flash.display.*
	import flash.events.*
	public class Main extends Sprite {
		private var sprite:Sprite = new Sprite();
		private var counter:int = 0;
		public function Main() 
		{ 
			super();
			addChild(sprite);
			sprite.graphics.beginFill(0x00CCFF);
			sprite.graphics.drawCircle(200, 200, 200);
			sprite.graphics.endFill();
			sprite.addEventListener(Event.ENTER_FRAME, handler);
		}
		private function handler(event:Event):void
		{
			sprite.scaleX = sprite.scaleY = (100 - counter) / 100;
			sprite.x = sprite.y = counter++ * 2;
			if (counter >= 100)
			{
				removeChild(sprite);
				sprite.removeEventListener(Event.ENTER_FRAME, handler);
			}
		}
	}
}