title: Silverlight WebContext is shared between mutipale sessions
body: <p>I have a silverlight Ria application . I use the WebContext to make the authentication staff. 
  I have these line in the App.cs constructor (it already come with the silverlight business teplate) :
   InitializeComponent();       </p>
  
  <p>WebContext webContext = new WebContext();<br>
   webContext.Authentication = new FormsWithTimeoutAuthentication(20);          </p>
  
  <p>this.ApplicationLifetimeObjects.Add(webContext);</p>
  
  <p>I face a problem , when I open the application in one browser tab , every thing is ok , I try to open another tab and to log in with different user it affect the application in the first tab .
  I traced the WebContext hashcode and get the same thing. So the WebContext seems to be shared on the both application instances. </p>
  
  <p>Do you have any idea why this happen ?
  Thanks in advance ...</p>