Отдельные сеансы с использованием элементов управления aXWebBrowser в приложении WinForms?

Из того, что я мог сказать, до тех пор, пока каждый браузер загружается в тот же поток, IE всегда будет рассматривать их как один и тот же сеанс.

Я обошел эту проблему, создав новый поток и новое окно для каждого сеанса.

static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    private static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);

        //// How many test windows do we need to create.
        int numberOfClients = 5;
        System.Threading.Thread[] threads = 
            new System.Threading.Thread[numberOfClients];

        //// Create threads for each of the windows, and then start them.
        for (int i = 0; i < numberOfClients; i++)
        {
            threads[i] = new System.Threading.Thread(Program.StartTest);
            threads[i].SetApartmentState(System.Threading.ApartmentState.STA);
            //// Passing in the startup parameters for each each instance.
            threads[i].Start(new StartupParameters(i));
        }

        //// This will keep the application running until 
        ////  all the windows are closed.
        foreach (System.Threading.Thread thread in threads)
        {
            thread.Join();
        }
    }

    /// <summary>
    /// Starts the test form.
    /// </summary>
    /// <param name="state">
    /// The state object containing our startup parameters.
    /// </param>
    private static void StartTest(object state)
    {
        StartupParameters parameters = state as StartupParameters;
        YourTestForm yourTestForm = new YourTestForm();

        //// Set the needed parameters before we run the form.  
        //// Add your parameters here.
        yourTestForm.Text = string.Format("Test form {0}", parameters.Index);

        //// Run the test.
        Application.Run(yourTestForm);
    }
}

/// <summary>
/// Contains the startup parameters used to configure 
/// each new instance of the test form.
/// </summary>
public class StartupParameters
{
    /// <summary>
    /// Initializes a new instance of the <see cref="StartupPramitures"/> class.
    /// </summary>
    /// <param name="index">The index.</param>
    public StartupParameters(int index)
    {
        this.Index = index;
    }

    /// <summary>
    /// The index for this test form.
    /// </summary>
    public int Index { get; private set; }
}