popup window open / close / minimize internalframe is disabled

the popup to restore / move / minimize / close / maximize Does not work, any solution?

my code to insert the form to my JDesktopPane is the sgt:

 frmEntregaMovil t = new frmEntregaMovil();

 JInternalFrame internalFrame = new JInternalFrame();

 internalFrame.setContentPane(t.getContentPane());

 internalFrame.pack();

 internalFrame.setVisible(true);

 jDesktopPane1.add(internalFrame);

   ? :/