title: Random "namespace name 'Core' does not exist in namespace ' Tweetinvi"
body: <p>I'm using the Tweetinvi C# Twitter API. It was working great until about 3 hours ago, when my solution (specifically one project) just stopped building.</p>
  
  <p>The error is a normal Assembly/Reference missing error, but I can see the files listed in the "references" folder. If i refresh the project, the errors go away. Until i build, then they come back.</p>
  
  <p>This is the same as <a href="https://stackoverflow.com/questions/5825867/random-assembly-references-fail-are-you-missing-a-using-directive-or-an-assemb">this post</a>, but my project does not target the client profile, its targets .NET 4 (Project>Properties>Application>Target Framework, right?), like it did this morning, like it did yesterday.</p>
  
  <p>I've uninstalled and reinstalled the Tweetinvi package via Nuget. Removed the references and re-added manually. No change.</p>
  
  <p>EDIT:
  To keep the crazy up, if i go to the Object Browser, and view by Namespace, there is only {}Tweetinvi.Security. If i refresh the project, i get them ALL back. Until I build.</p>
  
  <p>EDIT2:
  One of the warnings i get on build.</p>
  
  <blockquote>
    <p>The primary reference "Tweetinvi, Version=0.9.3.3, Culture=neutral,
    processorArchitecture=MSIL" could not be resolved because it has an
    indirect dependency on the framework assembly "System.Threading.Tasks,
    Version=2.5.19.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"
    which could not be resolved in the currently targeted framework.
    ".NETFramework,Version=v4.0". To resolve this problem, either remove
    the reference "Tweetinvi, Version=0.9.3.3, Culture=neutral,
    processorArchitecture=MSIL" or retarget your application to a
    framework version which contains "System.Threading.Tasks,
    Version=2.5.19.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a".</p>
  </blockquote>