Problem with PCL projects and MvvmCross

Resharper 8.1.14.21 fails on several files with a PCL project and installing latest version of MvvmCross from nuget. But not when installed. You must close VS 2013 and open again.

Steps to reproduce:

- Open VS2013
- Create a new PCL project (I select the defaults) (name it "Resharper.Core")
- Manage NuGet Packages
- Install MvvmCross package
- Save and exit
- Open VS2013
- Open the project
- Open ViewModels\FirstViewModel.cs and there you have. The error message is "Module 'System, Version=2.0.5.0, ........ ' should be referenced"

The project compiles ok.