error: Attempt to access a dead clipboard

Can anybody tell me what can be the cause of this error or where can I find out more about this error?

    event.preventDefault(); 

    try{ 
     var itemsVector:Vector.<Object> = 
event.dragSource.dataForFormat('itemsByIndex') as Vector.<Object>;
    }
     catch(errObject:Error) {
     trace(errObject.message);  
    }

---

It is with AIR, and happens when I try to drag items in a spark list.

Error: Attempt to access a dead clipboard
    at flash.desktop::Clipboard/checkAccess()
    at flash.desktop::Clipboard/getData()
    at DragDataFormatFetcher/getClipboardData()[E:\dev\4.0.0\frameworks\projects\airframework\src\mx\managers\NativeDragManagerImpl.as:953]
    at mx.core::DragSource/dataForFormat()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\DragSource.as:199]
    at components::TLComponent/lst_dragOverHandler()[C:\Users\Artur\Documents\My Dropbox\Projects\DS\Flash\src\components\TLComponent.mxml:111]
    at components::TLComponent/__lst_dragOver()[C:\Users\Artur\Documents\My Dropbox\Projects\DS\Flash\src\components\TLComponent.mxml:154]
    at flash.events::EventDispatcher/dispatch开发者_开发问答EventFunction()
    at flash.events::EventDispatcher/dispatchEvent()
    at mx.core::UIComponent/dispatchEvent()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\UIComponent.as:12266]
    at spark.layouts.supportClasses::LayoutBase/dragScroll()[E:\dev\4.0.0\frameworks\projects\spark\src\spark\layouts\supportClasses\LayoutBase.as:1773]
    at flash.utils::Timer/_timerDispatch()
    at flash.utils::Timer/tick()