Problem with custom popup window not working when going from one view model to another and back

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C#

WPF

MVVM

POP3

I am working with WPF in VS 2012 with C# utilizing the MVVM paradigm. So when I found this article
Custom popup and windows in WPF the MVVM way I was very excited and have used it extensively.

I create my applications using the ApplicationView to load up my different view models each of which is a user control. So Each user control has a button on the left and each operates independently.

My problem comes in when using the Custom popup as describe in the article above. The popup works fine when I am in one user control. Then when I click on the button to go to the other user control and do whatever over there and then come back to the previous view the popup no longer works.

I have stepped through the code and done everything I can think of including modifying the custom popup window dll. But with no luck. I am sure many people have used this control because it is really a great control.

Hopefully enough people out there have used this control and design their apps in a similar fashion so as to understand what I am describing.

My application view looks like so

<Window x:Class="PremierCareFinance.ApplicationView"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:local="clr-namespace:PremierCareFinance"  
         xmlns:cancelled="clr-namespace:PremierCareFinance.CancelledOrders"
        
         xmlns:wpfx="http://schemas.xceed.com/wpf/xaml/toolkit"       
        Title="Premier Care Finance" Height="800" Width="1280" Icon="finance.ico">

   
    <Window.Resources>
        <DataTemplate DataType="{x:Type local:HomeViewModel}">
            <local:HomeView />
        </DataTemplate>
        <DataTemplate DataType="{x:Type local:CustomerViewModel}">
            <local:CustomerView />
        </DataTemplate>
        <DataTemplate DataType="{x:Type cancelled:CancelledOrderViewModel}">
            <cancelled:CancelledOrderView  />  
        </DataTemplate>
      
    </Window.Resources>
    <Grid>
        <DockPanel>
        <Border DockPanel.Dock="Left" BorderBrush="Black" BorderThickness="0,0,1,0">
            <ItemsControl ItemsSource="{Binding PageViewModels}" >
                <ItemsControl.ItemTemplate>
                    <DataTemplate >

                        <Button Content="{Binding Name}" 
                                Command="{Binding DataContext.ChangePageCommand, RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
                                CommandParameter="{Binding }"  Margin="2,5"/>

                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
        </Border>

        <ContentControl Content="{Binding CurrentPageViewModel}" />
    </DockPanel>
     
   
    </Grid>
</Window>

Then all of my views are UserControls and I utilize tabs quite a bit.

Any help is appreciated