Please Help! Drag and drop does not work in Adobe AIR 3.1 (FlashBuilder 4.6)

I am working on a PC is made of air and flashbuilder 4.6.

Drag and drop application does not work in Flash Builder 4.6.

However, the same source will work with Flash Builder 4.5.

Please help me.

<?xml version="1.0" encoding="utf-8"?><s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"                              xmlns:s="library://ns.adobe.com/flex/spark"                              xmlns:mx="library://ns.adobe.com/flex/mx"                              backgroundColor="#323232" width="100%" height="100%"                              initialize="init(event)"                              nativeDragEnter="onDragEnter(event)"                              nativeDragDrop="onDragDrop(event)">          <fx:Script>          <![CDATA[                    import mx.events.FlexEvent;                    protected function init(event:FlexEvent):void                    {                              addEventListener(NativeDragEvent.NATIVE_DRAG_ENTER, onDragEnter);                              addEventListener(NativeDragEvent.NATIVE_DRAG_DROP, onDragDrop);                    }                    private function onDragEnter(event:NativeDragEvent):void                    {                              if (event.clipboard.hasFormat(ClipboardFormats.FILE_LIST_FORMAT))                              {                                        NativeDragManager.acceptDragDrop(this);                              }                    }                    private function onDragDrop(event:NativeDragEvent):void                    {                              var arr:Array;                              arr = Array(event.clipboard.getData(ClipboardFormats.FILE_LIST_FORMAT));                              startImage.source = (arr[0] as File).url;                    }            ]]>          </fx:Script>          <s:layout>                    <s:VerticalLayout/>          </s:layout>          <s:BorderContainer id="bc" borderStyle="solid" width="200" height="80%"/>          <s:Image id="startImage" width="100%" height="100%"                                         horizontalAlign="center" verticalAlign="middle"/>  </s:WindowedApplication>