RouteTask Solve Error

[Uoo]

Error:
Routing error: Unable to complete  operation.,Location "Location 1" in "Stops" is unlocated.  Location "Location 2" in "Stops" is unlocated.  Need at least 2 valid stops.  "Stops" does not contain valid input for any route.

Code:
ArcGis for Silverlight Samples (RoutingBarriers)-Is the same as
new RouteTask("http://tasks.arcgisonline.com/ArcGIS/rest/services/NetworkAnalysis/ESRI_Route_NA/NAServer/Route");

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Silverlight 5
Arcgis for Silverlight sdk 3.1