Obsolete nuget in project.
Sometimes a Visual Studio project will report the error "The schema version of '[Some Component]' is incompatible with version N.N.NNNNN.NNN of NuGet. Please upgrade NuGet to the latest version." The message is not talking about your Visual Studio version of NuGet! Instead, within the .nuget subfolder of your project there is an obsolete version of nuget.exe.
The fix is easy... drop to the command line, change to \your\project\path\.nuget and run
nuget.exe update -self
Rebuild your project and the errors will vanish.