I tried to open the project you have attached here with no luck.
\200523_silverlightapplication20\SilverlightApplication20\SilverlightApplication20.csproj : error : Unable to read the project file 'SilverlightApplication20.csproj'.
\200523_silverlightapplication20\SilverlightApplication20\SilverlightApplication20.csproj(120,3): The imported project "C:\Program Files\MSBuild\Microsoft\Silverlight\v4.0\Microsoft.Silverlight.CSharp.targets" was not found. Confirm that the path in the <Import> declaration is correct, and that the file exists on disk.
Can you please help me solve this issue?