强制转换类型失败，这是什么原因。该如何处理

强制转换类型失败，这是什么原因。。
TypeError: Error #1034: 强制转换类型失败:无法将 mx.managers::BrowserManagerImpl@d68e241 转换为 mx.managers.IBrowserManager。
at mx.managers::BrowserManager$/getInstance()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\BrowserManager.as:73]
at mx.managers::HistoryManagerImpl()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\HistoryManagerImpl.as:270]
at mx.managers::HistoryManagerImpl$/getInstance()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\HistoryManagerImpl.as:215]
at mx.core::Singleton$/getInstance()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\core\Singleton.as:113]
at mx.managers::HistoryManager$/get impl()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\HistoryManager.as:96]
at mx.managers::HistoryManager$/register()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\HistoryManager.as:134]
at mx.containers::ViewStack/commitProperties()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\containers\ViewStack.as:649]
at mx.containers::TabNavigator/commitProperties()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\containers\TabNavigator.as:504]
at mx.core::UIComponent/validateProperties()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\core\UIComponent.as:5807]
at mx.managers::LayoutManager/validateClient()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\LayoutManager.as:811]
at mx.managers::PopUpManagerImpl/addPopUp()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\PopUpManagerImpl.as:347]
at mx.managers::PopUpManager$/addPopUp()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\PopUpManager.as:169]
at com.jrosion.comas::PopUpEffect$/Show()[E:\work\spms\flex-src\com\jrosion\comas\PopUpEffect.as:35]
at com.jrosion.view::DisKrSpPutStorage/editRecord()[E:\work\spms\flex-src\com\jrosion\view\DisKrSpPutStorage.mxml:67]
at com.jrosion.view::DisKrSpPutStorage/__edit_click()[E:\work\spms\flex-src\com\jrosion\view\DisKrSpPutStorage.mxml:90]


------解决方案--------------------
我这怎么不出错呢。。。
看你的错误信息有at mx.managers::PopUpManagerImpl/addPopUp()
有popup的动作，这块是怎么写的？
------解决方案--------------------
在application中加入

import mx.managers.IBrowserManager;
import mx.managers.BrowserManager;

private var ibm:IBrowserManager=null;
private var bm:BrowserManager=null;