New Post: Exception when run the View Switching QuickStart

I am a fresher for PRISM. I hope I can get help from here regarding an exception I got when I run the View-Switching Navigation QuickStart from the folder \Source\Quickstarts\View-Switching Navigation\Silverlight\View-Switching Navigation.

The exception message said "An Unhandled Exception('Unhandle Exception SliverLight Appliction...) Code 4004. ModuleTypeLoadingException.

It seems like an exception regarding the Module Loading.
I didn't change anything in the solution, and the following is the xaml file(ModulesCatalog.xaml):

<Modularity:ModuleCatalog xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

                      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
                      xmlns:sys="clr-namespace:System;assembly=mscorlib" 
                      xmlns:Modularity="clr-namespace:Microsoft.Practices.Prism.Modularity;assembly=Microsoft.Practices.Prism">
<Modularity:ModuleInfoGroup Ref="ViewSwitchingNavigation.Contacts.xap" InitializationMode="WhenAvailable">
    <Modularity:ModuleInfo ModuleName="ContactsModule"/>
</Modularity:ModuleInfoGroup>
<Modularity:ModuleInfoGroup Ref="ViewSwitchingNavigation.Email.xap" InitializationMode="WhenAvailable">
    <Modularity:ModuleInfo ModuleName="EmailModule" />
</Modularity:ModuleInfoGroup>
<Modularity:ModuleInfoGroup Ref="ViewSwitchingNavigation.Calendar.xap" InitializationMode="WhenAvailable">
    <Modularity:ModuleInfo ModuleName="CalendarModule"/>
</Modularity:ModuleInfoGroup>

</Modularity:ModuleCatalog>

It looks correct to me.

Any suggestion with the exception are welcome and appreciated.

BTW, the environment I open the solution is PRISM 4/.Net 4/ SL 5, and I also tried change the target SL version to SL4, doesn't work and more errors about reference.

Thanks,
Kevin