I suggest you add a default symbol to your unique value renderer, so we will know if the issue is coming from the values of your attribute 'TYPE'.
<esri:SimpleMarkerSymbol x:Key="BLUEMarkerSymbol" Color="Blue" Size="12" Style="Circle" />
<esri:SimpleMarkerSymbol x:Key="PURPLEMarkerSymbol" Color="Purple" Size="12" Style="Circle" />
<esri:UniqueValueRenderer x:Key="MyUniqueValueRenderer" Attribute="TYPE" DefaultSymbol="BLUEMarkerSymbol" >
<esri:UniqueValueRenderer.Infos>
<esri:UniqueValueInfo Value="Church" Symbol="{StaticResource PURPLEMarkerSymbol}" />
<esri:UniqueValueInfo Value="SCHOOL" Symbol="{StaticResource PURPLEMarkerSymbol}" />
</esri:UniqueValueRenderer.Infos>
</esri:UniqueValueRenderer>
<esri:UniqueValueRenderer x:Key="MyUniqueValueRenderer" Attribute="TYPE" DefaultSymbol="{StaticResource BLUEMarkerSymbol}">
<esri:UniqueValueRenderer.Infos>
<esri:UniqueValueInfo Value="Church" Symbol="{StaticResource BLUEMarkerSymbol}" />
<esri:UniqueValueInfo Value="SCHOOL" Symbol="{StaticResource PURPLEMarkerSymbol}" />
</esri:UniqueValueRenderer.Infos>
</esri:UniqueValueRenderer>
selectedGraphic.Symbol = TryCast(LayoutRoot.Resources("StrobeMarkerSymbol_Blue"), ESRI.ArcGIS.Client.Symbols.Symbol)
<!-- UNIQUE VALUE RENDERER -->
<esri:SimpleMarkerSymbol x:Key="BLUEMarkerSymbol" Color="Blue" Size="12" Style="Circle" />
<esri:SimpleMarkerSymbol x:Key="PURPLEMarkerSymbol" Color="Purple" Size="12" Style="Circle" />
<esri:UniqueValueRenderer x:Key="MyUniqueValueRenderer" Attribute="TYPE" DefaultSymbol="{StaticResource BLUEMarkerSymbol}">
<esri:UniqueValueRenderer.Infos>
<esri:UniqueValueInfo Value="Church" Symbol="{StaticResource PURPLEMarkerSymbol}" />
<esri:UniqueValueInfo Value="SCHOOL" Symbol="{StaticResource PURPLEMarkerSymbol}" />
</esri:UniqueValueRenderer.Infos>
</esri:UniqueValueRenderer>
<esri:GraphicsLayer ID="MyGraphicsLayerBufferResults"
MouseEnter="imageBuffer_Mousehover"
MouseLeftButtonDown="GraphicsLayerBuffer_MouseLeftButtonDown"
Renderer="MyUniqueValueRenderer"
>
<esri:GraphicsLayer.MapTip>
<Border esri:GraphicsLayer.MapTipHideDelay="00:00:01.5" CornerRadius="10"
BorderBrush="#FF222957" BorderThickness="3" Margin="0,0,15,15">
<Border.Background>
<LinearGradientBrush EndPoint="1.038,1.136" StartPoint="0.015,0.188">
<GradientStop Color="#FFD1DFF2"/>
<GradientStop Color="#FF092959" Offset="0.946"/>
</LinearGradientBrush>
</Border.Background>
<Border.Effect>
<DropShadowEffect ShadowDepth="10" BlurRadius="14" Direction="300" />
</Border.Effect>
<StackPanel Orientation="Vertical">
<StackPanel Orientation="Horizontal">
<TextBlock Text="Distance: " FontWeight="Bold" HorizontalAlignment="Left" VerticalAlignment="Bottom" />
<TextBlock Text="{Binding [BUFFER_DISTANCE]}" HorizontalAlignment="Left" VerticalAlignment="Center" />
<TextBlock Text=" meters from parcel" HorizontalAlignment="Left" VerticalAlignment="Bottom" />
</StackPanel>
</StackPanel>
</Border>
</esri:GraphicsLayer.MapTip>
</esri:GraphicsLayer>
Private Sub QueryTask_ExecuteCompletedBuffer2(ByVal sender As Object, ByVal args As QueryEventArgs)
Dim featureSet As FeatureSet = args.FeatureSet
If args.FeatureSet.Features.Count < 1 Then
MessageBox.Show("No features found")
Return
End If
For Each selectedGraphic As Graphic In args.FeatureSet.Features
' Commented out
' selectedGraphic.Symbol = TryCast(LayoutRoot.Resources("StrobeMarkerSymbol_Blue"), ESRI.ArcGIS.Client.Symbols.Symbol)
_resultsGraphicsLayer.Graphics.Add(selectedGraphic)
Next selectedGraphic
<esri:SimpleFillSymbol x:Key="MyYellowFillSymbol" Fill="#44FFFF00" BorderBrush="Transparent" BorderThickness="2" />
<esri:SimpleFillSymbol x:Key="MyRedFillSymbol" Fill="#44FF0000" BorderBrush="Transparent" BorderThickness="2" />
<esri:SimpleFillSymbol x:Key="MyBlueFillSymbol" Fill="Blue" BorderBrush="Transparent" BorderThickness="2" />
<esri:ClassBreaksRenderer x:Key="MyClassBreaksRenderer" Attribute="PRECINCTS_" DefaultSymbol="{StaticResource MyRedFillSymbol}">
<esri:ClassBreaksRenderer.Classes>
<esri:ClassBreakInfo MinimumValue="0.0000" MaximumValue="8.0000" Symbol="{StaticResource MyYellowFillSymbol}" />
<esri:ClassBreakInfo MinimumValue="8.0001" MaximumValue="15.0000" Symbol="{StaticResource MyRedFillSymbol}" />
<esri:ClassBreakInfo MinimumValue="15.0001" MaximumValue="50.0000" Symbol="{StaticResource MyBlueFillSymbol}" />
</esri:ClassBreaksRenderer.Classes>
</esri:ClassBreaksRenderer>
<esri:FeatureLayer ID="MG_PrecinctsClassBreak"
Url="http://gis.logis.org/arcgis/rest/services/MG_Test/MapServer/6"
Renderer="{StaticResource MyClassBreaksRenderer}"
OutFields="PRECINCTS_" />