EntityFramework 6.1 cannot connect

I have a class library I have been using for over a year that has recently stopped working after upgrading to EF 6.1.

I have tried various methods for passing in the connect string to my Context class constructor but while it seems to correctly pass the string I invariably receive:

'(((System.Data.Entity.DbContext)(context)).Database.Connection).ServerVersion' threw an exception of type 'System.InvalidOperationException'

and the connection state stays closed.

Here is my AppConfig:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>

    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 --></configSections>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0" />
  </startup>
  <connectionStrings>
    <add name="MyContext" connectionString="Data Source=Server;Initial Catalog=DBName;Integrated Security=True;MultipleActiveResultSets=True" providerName="System.Data.SqlClient" />
  </connectionStrings>
  <entityFramework>
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
  </entityFramework>
</configuration>

My test class:

using System.Data.Entity;

namespace SVMIC.IMS.Entity.IMSClaim
{
    public class Context:DbContext
    {
        static Context()
        {
            Database.SetInitializer<Context>(null);
        }

        public Context():base("MyContext")
        {
        }
    }
}

and my test app:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using SVMIC.IMS.Entity.IMSClaim;

namespace TestApp
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();

      Context context = new Context();

    }
  }
}

The database server is SQL Server 2008 R2.

I assume it is something simple changed in 6.1 and I am just missing it, but I am totally stumped.