How To Connect To DB With Username And Passwd?

Hi I've created a login in my SQL Server 2005 like this:

CREATE LOGIN testuser
WITH PASSWORD = 'TestPWD';
USE DB1;
CREATE USER testuser FOR LOGIN testuser;
GO

now i want to connect from a c# app with the following connection STring
"Data Source=TURM21;Initial Catalog= Db1; Database= Db1 ; USER = testuser; PASSWORD = TestPWD; pooling=false; "

and i get the following Exception:
SqlConnection Handle : System.Data.SqlClient.SqlException: 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.)

CAn somebody help me? Whats wrong? Is it my connection string?

Greetz