A Connection Was Successfully Established With The Server, But Then An Error Occurred During The Login Process. (provider: Shared Memory Provider, Error: 0 - No Process Is On The Other End Of The Pipe.)

i'm going nuts with SQL server notification thing. I have gone throigh this artical which tells how to set user http://www.codeproject.com/KB/database/SqlDependencyPermissions.aspx. This article show how to create new user and setup for sql server notification.But In my case user was alredy existing in database. which is very common senario in most cases. So i did following( check the SQL script below) but then i get this error

"A connection was successfully established with the server, but then an error occurred during the login process. (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe.)"

this my sql script

use [master]
Go

-- Ensuring that Service Broker is enabled
ALTER DATABASE [DatabaseName] SET ENABLE_BROKER
GO

-- Switching to our database
use [DatabaseName]
GO

CREATE SCHEMA schemaname AUTHORIZATION username
GO

ALTER USER username WITH DEFAULT_SCHEMA = schemaname
GO

/*
 * Creating two new roles. We're not going to set the necessary permissions
 * on the user-accounts, but we're going to set them on these two new roles.
 * At the end of this script, we're simply going to make our two users
 * members of these roles.
 */
EXEC sp_addrole 'sql_dependency_subscriber'
EXEC sp_addrole 'sql_dependency_starter'

-- Permissions needed for [sql_dependency_starter]
GRANT CREATE PROCEDURE to [sql_dependency_starter]
GRANT CREATE QUEUE to [sql_dependency_starter]
GRANT CREATE SERVICE to [sql_dependency_starter]
GRANT REFERENCES on
CONTRACT::[http://schemas.microsoft.com/SQL/Notifications/PostQueryNotification]
  to [sql_dependency_starter]
GRANT VIEW DEFINITION TO [sql_dependency_starter]

-- Permissions needed for [sql_dependency_subscriber]
GRANT SELECT to [sql_dependency_subscriber]
GRANT SUBSCRIBE QUERY NOTIFICATIONS TO [sql_dependency_subscriber]
GRANT RECEIVE ON QueryNotificationErrorsQueue TO [sql_dependency_subscriber]
GRANT REFERENCES on
CONTRACT::[http://schemas.microsoft.com/SQL/Notifications/PostQueryNotification]
  to [sql_dependency_subscriber]

-- Making sure that my users are member of the correct role.
EXEC sp_addrolemember 'sql_dependency_starter', 'username'
EXEC sp_addrolemember 'sql_dependency_subscriber', 'username'