Justin, The issue is in your XML syntax:Yours<operationallayers>
<layer label="All-Island Deprivation Index" type="dynamic" visible="true" alpha="0.65"
url="http://na-lap-347/ArcGIS/rest/services/AI_DeprivationIndex/MapServer">
<sublayer id="0" popupconfig="popups/PopUp_Deprivation.xml" />
</layer>
<layer label="Sales 2-Bed Terrace 2007" type="dynamic" visible="false" alpha="0.65"
url="http://na-lap-347/ArcGIS/rest/services/Sales_2BedTerrace_07/MapServer" />
<sublayer id="0" popupconfig="popups/PopUp_2BedSales.xml" />
</layer>
</operationallayers>
The / at the end of your layer tag tell the XML that there is nothing else to follow that is a child of that layer element which is wrong.Correct<operationallayers>
<layer label="All-Island Deprivation Index" type="dynamic" visible="true" alpha="0.65"
url="http://na-lap-347/ArcGIS/rest/services/AI_DeprivationIndex/MapServer">
<sublayer id="0" popupconfig="popups/PopUp_Deprivation.xml" />
</layer>
<layer label="Sales 2-Bed Terrace 2007" type="dynamic" visible="false" alpha="0.65"
url="http://na-lap-347/ArcGIS/rest/services/Sales_2BedTerrace_07/MapServer">
<sublayer id="0" popupconfig="popups/PopUp_2BedSales.xml" />
</layer>
</operationallayers>