Wcf ria services stops working when running silverlight enabled WCF service

Dear Gurus!

I try to add silverlight enabled wcf service to my silverlight application in which I use wcf ria services.  When I start service my wcf ria services stop working   (sometimes it worked, sometimes - not). In my wcf service I use Service Broker For notification of changes in MSSQL database. Here is silverlight enabled wcf service:

    [ServiceContract(Namespace = "")]
    [SilverlightFaultBehavior]
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
    public class eventService
    {

        [OperationContract]
        public void StartTrackingChanges()
        {
            string connectionString = @"Server=serverName; Initial Catalog=road; 
                                                User ID =dependency_client; Password =111111; 
                                                Trusted_Connection =False; Integrated Security=True; ";

            SqlDependency.Stop(connectionString);
            SqlDependency.Start(connectionString);
        }
        [OperationContractAttribute(AsyncPattern = true)]
        public IAsyncResult BeginServiceAsyncMethod(string msg, AsyncCallback callback, object asyncState)
        {
            return new CompletedAsyncResult<emergEvent>(callback, asyncState);
        }

        public emergEvent EndServiceAsyncMethod(IAsyncResult r)
        {
            CompletedAsyncResult<emergEvent> result = r as CompletedAsyncResult<emergEvent>;
            emergEvent ev = new emergEvent();
            ev.TimeDetected = DateTime.Now;
            return ev;
        }

    class CompletedAsyncResult<T> : AsyncResult
    {

        T data;
        //bool complete = false;
        private const string connectionString = @"Server=serverName; Initial Catalog=road; 
                                                User ID =dependency_client; Password =111111; 
                                                Trusted_Connection =False; Integrated Security=True; ";

public CompletedAsyncResult(AsyncCallback callback, object state) : base(callback, state)
{
    AddEventChanges();
}
public void AddEventChanges()
{
  using (SqlConnection connection = new SqlConnection(connectionString))
 {
    using (SqlCommand cmd = new SqlCommand("Select id_event,name,description from dbo.events", connection))
{
  cmd.Notification = null;
  SqlDependency dependency = new SqlDependency(cmd);
                    dependency.OnChange += new OnChangeEventHandler(WaitChange);
                    connection.Open();

                    try
                    {
                        using (SqlDataReader reader = cmd.ExecuteReader())
                        {
                        }
                    }
                    catch (Exception)
                    {
                        SqlDependency.Stop(connectionString);
                        SqlDependency.Start(connectionString);
                        using (SqlDataReader reader = cmd.ExecuteReader())
                        {
                        }

                    }

                }
            }
        }
public void WaitChange(object sender, SqlNotificationEventArgs e)
  {
    base.Complete(false);
  }
}

So I run the service on the client:

proxy = new eventServiceClient();
 proxy.ServiceAsyncMethodCompleted += new EventHandler<ServiceAsyncMethodCompletedEventArgs>(proxy_GetUserCompleted);


proxy.StartTrackingChangesAsync(); // start service broker
proxy.ServiceAsyncMethodAsync(""); // start waiting for changes

What could be the reason?