login creation problem

hi, i'm using the last ctp of sql server management studio to create a database to sql express and add a login that give access to that database.
i created the login, assigned the user to the database assignig db_onwer and public, setting the default database, and create the login.
if i browse inside the database i find the news user created, the login seem created fine and linked to the user of the database, but if i try to use the login data to connect to the database i obtain the message

Login failed for user 'sitogs'. The user is not associated with a trusted SQL Server connection. (.Net SqlClient Data Provider)

this happens with both management studio and a my asp.net application.
I followed the procedure i always used with enterprisa manager and sql server.
Im doing something wrong?

> try to use the login data to connect to the database i obtain the
> message >
> Login failed for user 'sitogs'. The user is not associated with a
> trusted SQL Server connection. (.Net SqlClient Data Provider) What does your connection string look like? Are you sure you are trying to use SQL auth and not windows auth? Sounds like you are relying on windows auth. A

|||the connection string is:

workstation id=XPNEW;packet size=4096;user id=sitogs;data source=XPLAP;persist security info=True;password=sitogs

and is working fine with sql server 2000 with sql server authentication, and i have the same problem if i open sql management studio, change to sql server authentication and insert userid and password

|||"Trusted connection" is synonymous with "Windows Authentication". Make sure you've selected SQL Authentication in the connection dialog and not Windows Authentication.