invalid pane on XTP_DPN_PANEMENUCLICK

Hi,
i need yor help please:

I want to handle XTP_DPN_PANEMENUCLICK. But when the lParam in this case doesn't point to a valid CXTPDockingPane.
What is wrong or how can i get the pane who sends the message?




LRESULT CMainFrame::OnDockingPaneNotify(WPARAM wParam, LPARAM lParam)
{
     CXTPDockingPane* pPane = (CXTPDockingPane*)lParam;

    switch ((int)wParam)
    {
       case XTP_DPN_SHOWWINDOW:
          // here pPane is valid
          break;

       case XTP_DPN_PANEMENUCLICK:
          // here pPane is invalid
          break;
    }
}

Thanks, that helps! But i could not find it in the documentation. Is there any description for these parameters?