Operation Failed An exception was thrown while initializing part “NuGet.PackageManagement.VisualStudio.VSSolutionManager”. GetFullVsVersionString must be called on the UI thread.

Visual Studio 2015 update 3 could throw this exception.

the way to fix it
1. open vs2015 and don’t open any project.
2. go to menu ‘Tools’ -> Nuget Package Manager -> Package Manager Setting
3. once you see dialog pop up successfully without error, click on ‘OK’ button to confirm.
4. open any project. now you could see that Nuget error is gone.