SharePoint 2010 - asp:CreateUserWizard

While using the asp:CreateUserWizard control to add forms based authentication users to my asp membership database I was encountering the following error:

Exception of type 'System.ArgumentException' was thrown.
Parameter name: encodedValue

The error above was being generated after I successfully created a new user.  The issue it seems is with the control creating a cookie named:  .ASPXAUTH

The solution expire the cookie.

private void ResetAuth()
{
  HttpCookie aspCookie = new HttpCookie(".ASPXAUTH");
  aspCookie.Expires = DateTime.Now.AddDays(-1);
  Response.Cookies.Add(aspCookie);            
}

This needs to be done on both the ContinueButtonClick and the onActiveStepChanged Event.

ActivateStepChanged

protected void ActiveStepChanged(object sender, EventArgs e)
{
   ResetAuth();   
}

ContinueButtonClick

protected void btnContinue_Clicked(object sender, EventArgs e)
{
   ResetAuth();
}

A more detailed explanation of this and other asp.net login control issues can be found here within Bernado Nguyen-Hoan's Blog