Importing a class works only in same folder

programming flash
1

I have a class I made for a seekbar that looks like this:

package {
	import com.utility.formating.FormatTime;
	import flash.display.MovieClip;
	import flash.text.TextField;	
	import flash.events.*;
	import flash.geom.Rectangle;
	import fl.video.VideoEvent;
        import fl.video.FLVPlayback;

	public class SeekBar extends MovieClip {
		public var flvplayback:Object;
		public var percentPlayheadTime:Number;
		public var currentPlayheadTime:Number;
		public var totalPlayheadTime:Number;		
		public var seekTotal:Number;
		public var seekWidth:Number;
		public var dragging:Boolean;
		
		public function SeekBar(flvplayback:Object) {
			this.flvplayback = flvplayback;
			this.flvplayback.playheadUpdateInterval = 100;
			this.flvplayback.autoRewind = false;
			this.seekWidth = this.seekBackground_mc.width;
			this.percentPlayheadTime = 0;
			
			this.seekButton_mc.buttonMode = true;
			this.seekButton_mc.useHandCursor = true;			
			this.updateSeekPosition();

			this.flvplayback.addEventListener(VideoEvent.PLAYHEAD_UPDATE, this.updateData);
			this.seekButton_mc.addEventListener(MouseEvent.MOUSE_DOWN, this.seekButtonMouseDown);
			this.flvplayback.stage.addEventListener(MouseEvent.MOUSE_UP, this.stageMouseUp);
		}
	}
}

When I put the .as file in the same folder as my .fla and link it in the library using SeekBar for the path, it works. If I move it to my main classpath and link it using com.video.SeekBar I get the following errors when I try to run it:

1119: Access of possibly undefined property seekBackground_mc through a reference with static type SeekBar.

Every reference to a movieclip is throwing the same error. Could someone explain what’s happening?