Additionally helpful reference material is provided below.
The core ArcGIS API for Silverlight v2.4, build 851 (v126.96.36.1991) encompasses many compelling features, improvements, and samples that may be of benefit to your development efforts which include the Business Analyst Online API for Silverlight. Unfortunately, the current Business Analyst Online API for Silverlight v2.2 is not compatible with the latest core ArcGIS API for Silverlight release.
While we are working on releasing the next version of the Business Analyst Online API for Silverlight, we are offering our customers the option to install and update their existing applications built against the Business Analyst Online API for Silverlight v2.2 so that they are compatible with the latest core ArcGIS API for Silverlight v188.8.131.521.
Quick Steps to Update Your Existing Business Analyst Online API for Silverlight v2.2 Visual Studio 2010 Solutions:
Install the core ArcGIS API for Silverlight (the most current version which is v184.108.40.2061) available here.
The core ArcGIS API for Silverlight v220.127.116.111 will be installed at either C:\Program Files (x86)\ESRI SDKs\Silverlight\v2.4 (64-bit CPU) or C:\Program Files\ESRI SDKs\Silverlight\v2.4 (32-bit CPU).
Download and install the Business Analyst Online API for Silverlight version 2.2 for Core ArcGIS API for Silverlight version 2.4.
The Business Analyst Online API for Silverlight v18.104.22.168 assembly will be installed at either C:\Program Files (x86)\ESRI SDKs\Silverlight\BAOnline\v2.2 (64-bit CPU) or C:\Program Files\ESRI SDKs\Silverlight\BAOnline\v2.2 (32-bit CPU).
Note: You may need to uninstall any previous Business Analyst Online API for Silverlight version 2.2 setup since is not compatible with core ArcGIS API for Silverlight v22.214.171.1241.
In your application code be sure to update and verify the version numbers of the following assembly references and clean/recompile your solution:
Note: Current Business Analyst Online API for Silverlight v2.2 sample application code and downloads will need to be updated.
This information applies to the ArcGIS API for Silverlight as well as the Business Analyst Online or Server APIs for Silverlight when downloading assemblies or Visual Studio 2010 solutions that contain assemblies. This important note is for your future reference.
As part as a security enhancement in Visual Studio 2010, you now need to “opt-in” to using/referencing certain assemblies/.dlls when they are downloaded and were not originally installed/registered on your system. If you get an error or warning about downloaded or blocked assemblies, you will need to manually unblock them before building and running the application within Visual Studio 2010.
See the following link for instructions on how to unblock an assembly for Visual Studio 2010:
http://go.microsoft.com/fwlink/?LinkId=179545. Basically you must shut down Visual Studio; right-click on the assemblies in question; select Properties from the popup dialog; click on “Unblock”; and reopen the Visual Studio solution. If the “Unblock” button is not available then the assembly is not being blocked by your system.