Property editing not available

I have lost the ability to edit properties using the property editor in VS 2010 Pro.

The XAML that shows this problems is:

<Window x:Class="MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:SMOExplorer"
    xmlns:smo="clr-namespace:Microsoft.SqlServer.Management.Smo;assembly=Microsoft.SqlServer.Smo"
    Title="MainWindow" Height="545" Width="971" Loaded="Window_Loaded"><Window.Resources><ResourceDictionary><ResourceDictionary.MergedDictionaries><ResourceDictionary Source="\Dictionaries\TableDictionary.xaml"></ResourceDictionary><ResourceDictionary Source="\Dictionaries\StoredProcedureDictionary.xaml"></ResourceDictionary><ResourceDictionary Source="\Dictionaries\ViewDictionary.xaml"></ResourceDictionary></ResourceDictionary.MergedDictionaries></ResourceDictionary></Window.Resources><Grid><Grid.RowDefinitions><RowDefinition Height="30"></RowDefinition><RowDefinition></RowDefinition></Grid.RowDefinitions><Grid.ColumnDefinitions><ColumnDefinition></ColumnDefinition><ColumnDefinition></ColumnDefinition></Grid.ColumnDefinitions><ComboBox SelectionChanged="ComboBox_SelectionChanged" ItemsSource="{Binding sqlserverList}" Grid.Row="0" Grid.Column="0"></ComboBox><TreeView Name="tvMain" TreeViewItem.Expanded="tvMain_Expanded" Grid.Row="1" Grid.Column="0"><TreeView.ItemTemplate><HierarchicalDataTemplate ItemsSource="{Binding Converter={StaticResource gli}}"><StackPanel Orientation="Horizontal"><TextBlock Text="{Binding Path=Name}"></TextBlock></StackPanel></HierarchicalDataTemplate></TreeView.ItemTemplate></TreeView><ContentControl x:Name="theContent" Grid.Row="1" Grid.Column="1" Content="{Binding Path=SelectedValue.Item, ElementName=tvMain}"></ContentControl></Grid></Window>

The lines that define the ResourceDictionaries have a blue squiggly line under them but when a compile happens that goes away but I still cannot edit the properties using the VS tools.

When I switch to the design window I can see an error:

Invalid URI: The format of the URI could not be determined.
   at System.Uri.CreateThis(String uri, Boolean dontEscape, UriKind uriKind)
   at System.Uri..ctor(String uriString, UriKind uriKind)
   at MS.Internal.Host.BinaryResourceImpl.get_FileUri()
   at MS.Internal.Host.MarkupProjectContext.GetBinaryResource(Uri uri)
   at Microsoft.Windows.Design.DocumentModel.MarkupDocumentManagerBase.TreeChangeListener.Microsoft.Windows.Design.DocumentModel.IDocumentTreeConsumer.HandleMessage(DocumentTreeCoordinator sender, MessageKey key, MessageArguments args)

TIA,

LS

Lloyd Sheen