RiaContext Authentication on IIS

Question

RiaContext.Current.Authentication.LoadUser().Completed += new EventHandler(User_Completed);
...
void User_Completed(object sender, EventArgs e) 
{
CapacityDomainContext _capacityContext = new CapacityDomainContext();
_capacityContext.GetSession().Completed += new EventHandler(Session_Completed); 
}

The code above works perfectly in visual studio webserver, but in iis RiaContext.User is null. whats wrong???