I have such error in vs 2012: NuGet Package restore failed for project Miscellaneous Files: Value cannot be null or an empty string. Parameter name: root. 0 0
I see
I right clicked the solution and chose "Enable Nuget Package Restore". This fixed the problem.
This link from MSDN shows how:
http://blogs.msdn.com/b/dotnet/archive/2013/06/12/nuget-package-restore-issues.aspx
nuget visual-studio