Setting the focus. it does fail

Hi all of you, I've got a couple of issues with the focus of my view.

I wonder whether related with PasswordBox control or not

The first issue:

  <PasswordBox Margin="48,14,56,14" x:Name="pwdnou" 
        FocusManager.FocusedElement="{Binding ElementName=pwdnou}"
            PasswordChanged="pwdnou_PasswordChanged"
                     
            Grid.ColumnSpan="2" Grid.Column="1" Foreground="MidnightBlue" BorderBrush="Gray" 
            HorizontalAlignment="Center" VerticalAlignment="Center" Height="24" Width="100" />

        <PasswordBox Margin="48,14,56,14" x:Name="pwdnouconfirmar" 
            Style="{StaticResource PasswordBoxVistaStyle}"
                   LostFocus="pwdnouconfirmar_LostFocus"
            Grid.ColumnSpan="2" Grid.Column="1" Foreground="MidnightBlue" BorderBrush="Gray" 
            HorizontalAlignment="Center" VerticalAlignment="Center" Height="24" Width="100" Grid.Row="1" />           

It does not work at all; when I load my view I don't see the cursor on "pwdnou" PasswordBox, in fact, the cursor is not visible at all.

Nevertheless if I write pwdnou.Focus() in OnLoaded Grid event code-behind it does works properly. But I don't like to use code-behind for that.

The second one is when I try to set the focus in that same PasswordBox from the Lostfocus event on the second one PasswordBox (pwdnouconfirmar). Here, amazingly does not work.

What am  I missing here?

 Private Sub pwdnouconfirmar_LostFocus(sender As Object, e As RoutedEventArgs)
        If pwdnou.Password <> pwdnouconfirmar.Password Then
            sMessageTranslated = My.Resources.MasterGIT.APP_ERROR3
            WpfMessageBox.Show(sMessageTranslated, Conectividad.NameOfApplication, WpfMessageBoxButton.OK, WpfMessageBoxImage.Error)
            pwdnou.Password = String.Empty
            pwdnouconfirmar.Password = String.Empty
'            pwdnou.Focusable = True
            pwdnou.Focus()



            'Exit Sub

        End If

Thanks in advance for any input or hint provided

Primary platform is Windows 7 Ultimate 64 bit along with VS 2012/Sql2k8 for WPF/SilverLight projects.