Error when using TileMapServiceLayer

RiverTaig1

First, I'll admit to being a total newbie!  Sorry. I'm getting an error in my Windows Phone / Silverlight application when I try to run it (using the Windows Phone Emulator if that makes a difference).

ArcGISTiledMapServiceLayer does not support Multi-Layer Caches. Use an ArcGISDynamicMapServiceLayer instead or create a single fused cache.

If I change the second layer to a DynamicMapServiceLayer, it works, but then it's not using the tiles that I set up, right? And performance will be much less than optimal.  I definately want to use tiles as I have some fairly complex labels that might be slow to draw otherwise. The error indicates that I should use a "fused cache"...when I go to the service properties for that MapService (AALOnWindowsPhone2), it *IS* using a single fused cache though. I'm not sure what a single fused cache is, but I'm assuming that means you just have one scale define (which I do at a scale of 1:3000).  

Any thoughts?  Here's the XAML:

  

         <esri:Map x:Name="MyMap" WrapAround="True" 
          SizeChanged="MyMap_SizeChanged" RenderTransformOrigin="0.5,0.5" >
                <esri:Map.RenderTransform>
                    <ScaleTransform ScaleX="2" ScaleY="2" />
                </esri:Map.RenderTransform>
                 <esri:ArcGISTiledMapServiceLayer ID="MyLayer" 
                    Url="http://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer" />
                <esri:ArcGISTiledMapServiceLayer ID="LocalLayer"  Url="http://sapphire/ArcGIS/rest/services/AALOnWindowsPhone2/MapServer" />
            </esri:Map>

RiverTaig1

In this case, my local map service just has one layer in it.  According to the service properties it is a "fused-cached".  In my XAML, the base map served up from ArcGISOnline is a tiled map service, and what I'm hoping to do is have my layer also be a tiled map service on top of the base map. That should be fine, right (two tiled map services in the same map)?  I'm using .png files, so they should be transparent (i.e. I should be able to see the ESRI basemap under my tiled images).