Strange Visual Studio 2013 errors

Question

I'm experiencing the following Visual Studio 2013 error in the next picture whenever I want to add a project reference:

This file exists in my hard disk.

Also, if I try to use a code snippet I get the following error:

For now, I've tried to reinstall Visual Studio 2013 and executing devenv /resetsettings command but it couldn't solve the whole problems.

Does someone experienced these errors and could solve them?

Answer 1

What caused the problem? Believe it or not, it was that I had Team Explorer 2013 installed before I decided to install Visual Studio 2013 Ultimate.

I did a trial-error uninstalling Team Explorer 2013, I rebooted my machine and bingo! This solved the whole problem...