Listview&Treeview drag event issue

Hi,

     The listview and treeview works normally in non-mdi application,such as code example 'w_employee_xfer'. But when I use them on a child window of mdi frame,and presses the left mouse button in the ListView(TreeView) control and begins dragging,the mouse pointer disappeared ,and never get back again.Why? Is it a bug of pb12.6?

     Thanks for your input!

Best Regards!

Marcus