ArcGIS Silverlight Viewer 3.1 Upgrade - The remote server returned an error. NotFound

[IanPeebles]

I just upgraded to ArcGIS Silverlight API 3.0 to 3.1 and the ArcGIS Silverlight Viewer from 3.0 to 3.1.  When trying to upgrade my applications, I am getting the following error message:

Anyone have any suggestions how to resolve this error?

I created a new application and copied code in from my 3.0 version application, but I could not utilize the functionality of the query related objects tool.

Looks like I have to create the application over again?

[ScottBailey]

I also had this error after installation. Its seems as thought the new install did not overwrite the previous 3.0 installation. I had to unstall 3.0 completely and then intall 3.1. After that it was fine.