Flow Right to Left Sub Menu opens to wrong direction - only in VS 2012

This code works prefect on Visual studio 2010

on Visual Studio 2012 the Sub Menu Aligns to the wrong side (as in LTR and not as it should be on RTL)

<Window x:Class="menutest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" FlowDirection="RightToLeft"><DockPanel><Menu DockPanel.Dock="Top"  HorizontalAlignment="Left" Height="40" VerticalAlignment="Top" Width="100"><MenuItem Header="בדיקה"><MenuItem Header="בדיקה ארוכה מאוד"></MenuItem><MenuItem Header="בדיקה ארוכה מאוד"></MenuItem><MenuItem Header="בדיקה ארוכה מאוד"></MenuItem></MenuItem></Menu></DockPanel></Window>

<window flowdirection="RightToLeft" height="350" title="MainWindow" width="525" x:class="menutest.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"><dockpanel><menu dockpanel.dock="Top" height="40" horizontalalignment="Left" verticalalignment="Top" width="100"><menuitem header="בדיקה"><menuitem header="בדיקה ארוכה מאוד"></menuitem><menuitem header="בדיקה ארוכה מאוד"></menuitem><menuitem header="בדיקה ארוכה מאוד"></menuitem></menuitem> </menu></dockpanel> </window>