Datagrid template column combobox selection dissapears after clicking on a different cell

Hello..

I have a datagrid and one of the columns is a template column with a combobox. The items in the datagrid and the combobox come from a collection. The datagrid collection has the .Include in the select statement because I don't want to show the ids but the related fields. When I click on the combobox it works fine, it does select the item I want, however, for some reason, once I click on another cell, the content dissapears... I know is there and has being selected because when I click back it shows up again.

Here is my datagrid collection:

       #region gettingAllDespachos
        public ObservableCollection<Despacho> getAllDespachos()
        {
            var despacho = (from d in context.Despachos.Include("Cliente").Include("Ruta").Include("Employee")
                            select d).ToList();
            return new ObservableCollection<Despacho>(despacho);
        }
        #endregion

Here is where I get the collection for my combobox:

        #region RutaComboBox
        public List<Ruta> RutasCombo
        {
            get
            {
                List<Ruta> listRuta = new List<Ruta>();
                var rutas = from r in context.Rutas select r;
                foreach (var item in rutas)
                {
                    Ruta ruta = new Ruta();
                    ruta.RutaID = item.RutaID;
                    ruta.RutaDescripcion = item.RutaDescripcion;
                    listRuta.Add(item);
                }
                return listRuta.OrderBy(r => r.RutaDescripcion).ToList();
            }
        }

HEre is XAML code:

<!--Ruta Combobox--><DataGridTemplateColumn x:Name="rutaColumn" Header="Ruta" Width="250" SortMemberPath="RutaID"><DataGridTemplateColumn.CellTemplate><DataTemplate><TextBlock Text="{Binding Ruta.RutaDescripcion}"  /><!--For some reason if I only select here the RutaID Primary Key it works!!--><!--<TextBlock Text="{Binding RutaID}"  />--></DataTemplate></DataGridTemplateColumn.CellTemplate><DataGridTemplateColumn.CellEditingTemplate><DataTemplate><ComboBox x:Name="rutaComboBox" SelectedValue="{Binding RutaID, NotifyOnSourceUpdated=True,Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnExceptions=True}" 
                                                  SelectedValuePath="RutaID" DisplayMemberPath="RutaDescripcion" HorizontalContentAlignment="Stretch"  
                                                  ItemsSource="{Binding RutasCombo, ElementName=ListarDespachosPG}" ><ComboBox.ItemContainerStyle><Style TargetType="{x:Type ComboBoxItem}"><Setter Property="Template"><Setter.Value><ControlTemplate><Grid><Grid.ColumnDefinitions><ColumnDefinition Width="50"/><ColumnDefinition Width="*"/></Grid.ColumnDefinitions><TextBlock Margin="5" Grid.Column="0" Text="{Binding RutaID}"/><TextBlock Margin="5" Grid.Column="1" Text="{Binding RutaDescripcion}"/></Grid></ControlTemplate></Setter.Value></Setter></Style></ComboBox.ItemContainerStyle></ComboBox></DataTemplate></DataGridTemplateColumn.CellEditingTemplate></DataGridTemplateColumn>

As you can see, in the datagridtemplatecolumn.celltemplate I'm using 

<TextBlock Text="{Binding Ruta.RutaDescripcion}"  />

But when I use this:

<TextBlock Text="{Binding RutaID}"  />

It works!! Hence, I think it has something to do with the fact that I want to show the description and not the ID....

Any help will be greatly appreciated...

Guisselle