DBExpress connecting SQL 2008 at runtime with Delphi 2009

Question

Hi,
I'm trying to connect at runtime with SQL Server 2008 with Delphi 2009 using DBExpress, it it's not working. When I set all the properties at design time, it works great, but at RunTime, I'm getting "unknown driver: mssql". Below is the code:

  scnConexao := TSQLConnection.Create(nil);
  scnConexao.DriverName := 'MSSQL';
  scnConexao.ConnectionName := 'MSSQLConnection';
  scnConexao.GetDriverFunc := 'getSQLDriverMSSQL';
  scnConexao.LibraryName := 'dbxmss.dll';
  scnConexao.VendorLib := 'oledb';
  scnConexao.LoginPrompt := False;
  scnConexao.Params.Add('SchemaOverride=sa.dbo');
  scnConexao.Params.Add('HostName=DESKTOP');
  scnConexao.Params.Add('DataBase=DBNAME');
  scnConexao.Params.Add('OS Authentication=False');
  scnConexao.Params.Add('User_Name=UserName');
  scnConexao.Params.Add('Password=Password');
  scnConexao.Params.Add('MSSQL TransIsolation=ReadCommited');
  scnConexao.Open;

I have included the dbxmss.dll in the same directory as my app, but to no avail. Any help would be greatly appreciated.
Tks