How can I load debugging symbols for System.Windows (Windows Phone)?

The thing is, I got a weird exception from Windows Phone app I am developing:

System.Exception was unhandled
Message=Unspecified error 
StackTrace:
   at MS.Internal.XcpImports.CheckHResult(UInt32 hr)
   at MS.Internal.XcpImports.Collection_AddValue[T](PresentationFrameworkCollection`1 collection, CValue value)
   at MS.Internal.XcpImports.Collection_AddDependencyObject[T](PresentationFrameworkCollection`1 collection, DependencyObject value)
   at System.Windows.PresentationFrameworkCollection`1.AddDependencyObject(DependencyObject value)
   at System.Windows.Controls.UIElementCollection.AddInternal(UIElement value)
   at System.Windows.PresentationFrameworkCollection`1.Add(UIElement value)
   at System.Windows.Controls.ItemsControl.AddVisualChild(Int32 index, DependencyObject container, Boolean needPrepareContainer)
   at System.Windows.Controls.ItemsControl.AddContainerForPosition(GeneratorPosition position)
   at System.Windows.Controls.ItemsControl.OnItemsChangedHandler(Object sender, ItemsChangedEventArgs args)
   at System.Windows.Controls.ItemContainerGenerator.OnItemAdded(Object item, Int32 index)
   at System.Windows.Controls.ItemContainerGenerator.System.Windows.Controls.ICollectionChangedListener.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
   at System.Windows.Controls.WeakCollectionChangedListener.SourceCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Windows.Controls.ItemCollection.NotifyCol开发者_JAVA百科lectionChanged(NotifyCollectionChangedEventArgs e)
   at System.Windows.Controls.ItemCollection.System.Windows.Controls.ICollectionChangedListener.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Windows.Controls.WeakCollectionChangedListener.SourceCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.InsertItem(Int32 index, FormItem item)
   at System.Collections.ObjectModel.Collection`1.Add(FormItem item)
   at //My Code

What my code tried to do is add a item to an ObservableCollection.

I want to step into System.Windows code so I can see what that "Unspecified error" is.

I already do the following in my Visual Studio:

• Enable .NET Framework source stepping
• Enable source server support
• Enable Microsoft Symbol Servers

Despite that, I can't step in (double clicking) into any of System.Windows methods in the call stack.

Any help is appreciated. Let me know if any of you need more clarification.