Problem Of Connection With Sqlserver2005

Hello,

I installed sqlserver2005_express on my PC (localhost) and I try to execute a sql query with ASP.NET.

Here's my page :
Dim mySqlConnection as SqlConnection = new SqlConnection("server=JOE10155SQLEXPRESS;Trusted_Connection=yes;UID=sa;PWD=xxxx;database=xxxx")
    Dim mySqlDataAdapter as SqlDataAdapter = new SqlDataAdapter("SELECT * FROM Entreprise WHERE (EntrepriseNr =999)", mySqlConnection)
    Dim myDataSet as DataSet = new DataSet()
    mySqlDataAdapter.Fill(myDataSet,"Entreprise")

The problem is :
System.Data.SqlClient.SqlException: Autorisation SELECT refusée sur l'objet 'Entreprise', base de données 'xxxx', schéma dbo'.

if someone have an idea?