Tim Van Wassenhove

Because Silverlight checks the origin it considers http://localhost and http://127.0.0.1 as different locations. In case you want your visitors to be able to use both addresses you can recalculate the address as following:

EndpointAddress GetEndpointAddress(EndpointAddress endpointAddress)
{
 var scheme = Application.Current.Host.Source.GetComponents(UriComponents.Scheme, UriFormat.Unescaped);
 var serverAndPort = Application.Current.Host.Source.GetComponents(UriComponents.HostAndPort, UriFormat.Unescaped);
 var pathAndQuery = endpointAddress.Uri.GetComponents(UriComponents.PathAndQuery, UriFormat.Unescaped);
 return new EndpointAddress(scheme + "://" + serverAndPort + pathAndQuery);
}

And you can use this method as following:

var client = new DirectoryServiceClient();
client.Endpoint.Address = GetEndpointAddress(client.Endpoint.Address);
client.GetMessageCompleted += ClientGetMessageCompleted;
client.GetMessageAsync();