Problem with Binding Multiple Objects on WPF

Question

Hi, I'm developing a user control called SearchBox, that will act as a replacer for ComboBox for multiple records, as the performance in ComboBox is low for this scenario, but I'm having a big binding problem.

I have a base control with a DependencyProperty called SelectedItem, and my SearchControl shows that control so that the user can select the record. The SearchControl also has a DependencyProperty called SelectedItem on it, and it is being updated when the user selects something on the base control, but the UI, wich has the SearchControl, is not being updated. I used a null converter so that I could see if the property was updating, but it's not. Below is some of the code: This is the UI:

<NectarControles:MaskedSearchControl x:Name="teste"
    Grid.Row="0" Grid.Column="1"
    Height="21"
    ItemsSource="{Binding C001_Lista}"
    DisplayMember="C001_Codigo"
    Custom:CustomizadorTextBox.CodigoCampo="C001_Codigo"
    ViewType="{x:Type C001:C001_Search}"
    ViewModelType="{x:Type C001_ViewModel:C001_ViewModel}"
    SelectedItem="{Binding Path=Instancia.C001_Holding, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource DebuggingConverter}}">
</NectarControles:MaskedSearchControl>

This is the relevante part of the SearchControl:

Binding selectedItemBinding = new Binding("SelectedItem");
selectedItemBinding.Source = this.SearchControlBase;
selectedItemBinding.Mode = BindingMode.TwoWay;
selectedItemBinding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
this.SetBinding(SelectedItemProperty, selectedItemBinding);

...

public System.Data.Objects.DataClasses.IEntityWithKey SelectedItem
{
  get
  {
    return (System.Data.Objects.DataClasses.IEntityWithKey)GetValue(SelectedItemProperty);
  }
  set
  {
    SetValue(SelectedItemProperty, value);
    if (PropertyChanged != null)
      PropertyChanged(this, new PropertyChangedEventArgs("SelectedItem"));
  }
}

Please someone help me...