Connection.ServerVersion Throws System.InvalidOperationException

I am using VWD2005 and SQLExpress 2005.  In web.config I define the connection:<connectionStrings>

<add name="ProFeeRevenueUser" connectionString="Data Source=.SQLEXPRESS;AttachDBFilename=|DataDirectory|ProFeeRevenue.mdf; Initial Catalog=ProFeeRevenue;User Id=whomever;Password=whatever" providerName="System.Data.SqlClient"/>

When I try this code in a class (util.cs), I get an error on trying to open the connection:System.Data.SqlClient.SqlConnection cn = new System.Data.SqlClient.SqlConnection(ConfigurationManager.ConnectionStrings["ProFeeRevenueUser"].ConnectionString);

System.Data.SqlClient.SqlCommand cmd = new System.Data.SqlClient.SqlCommand("usp_UserSystemRolesListByUser", cn);System.Data.SqlClient.SqlDataReader dr;

try

{cmd.CommandType = System.Data.CommandType.StoredProcedure;

System.Data.SqlClient.SqlParameter retValParm = cmd.Parameters.Add("@RowCount", System.Data.SqlDbType.Int);retValParm.Direction = System.Data.ParameterDirection.ReturnValue;cmd.Parameters.AddWithValue("@UserLogin", userLogin);

cn.Open();     // error occurs here  <<----------------------------

dr = cmd.ExecuteReader();if (dr.HasRows)

{while (dr.Read() == true)

{string MyRole = dr[1].ToString().Trim();

SystemRoles.Add(MyRole);

}

dr.Close();

}

 It works fine if I point to a SQL server database on my server, but not with SQLExpress, so I assume I have done something wrong with the connection string or the SQL Express database.  Any ideas?