Error 404: Not Found - Parallel Execution

I'm trying to run tests in parallel by using Nunit3.

  [Test]
  [Parallelizable(NUnit.Framework.ParallelScope.Self)]
    public void test()
    {
        foo();
    }

   [SetUp]
    public void Initialization()
    {

        InternetExplorerOptions caps = new InternetExplorerOptions();
        caps.IgnoreZoomLevel = true;
        caps.EnableNativeEvents = false;
        caps.EnablePersistentHover = true;
        caps.AddAdditionalCapability("browserstack.ie.enablePopups‌​", false);
        _webdriver = new RemoteWebDriver(new Uri("http://127.0.0.1:4422/wd/hub/"), caps.ToCapabilities());
        _webdriver.Navigate().GoToUrl("http://crmtest16:5555/CRMTLV/main.aspx");
         CloseDialog();
        _webdriver.Manage().Window.Maximize();
    }

I'm running my tests on IE11 browser and I'm getting the following error only when using the Parallelizable parameter.

OpenQA.Selenium.WebDriverException : Unexpected error. Error 404: Not Found

The browsers are being opened on both Nodes(selenium grid) and even navigating to the URL, but then it fails. What am I missing?