NuGet causing TFS authorization problems

I am correctly authorised with TFS, and I can check in changes etc. But when I try to get a package from Nuget I get the following error, and after that I get authorisation problems form every operation until I restart VS. What could be causing the i开发者_如何转开发ssue?

Try this out http://blog.rthand.com/post/2011/08/26/Fixing-combination-of-NuGet-and-Team-Foundation-in-workgroup-configuration-401-Unauthorized.aspx.