Dekho utilises an ArcGIS Server Geometry Service and will not function properly without calling the service. Dekho functionality like snapping and coordinate system readouts in multiple coordinate systems relies on the geometry service. Dekho stores the REST endpoint for the geometry service published by the primary instance of ArcGIS Server.
The release of ArcGIS Server 10.1 provided the Geometry Service pre-installed in the Utilities folder in the ArcGIS Server Manager. You will need to log into the Server Manager and start the Geometry Service.