User validation in Nav WebServices from Windows CE

Hi all

I have a problem with a user validation in a PDA that works with Windows CE. i have a visual basic application that must logged in nav by WebServices but it can´t and bring me a not permission error ("The Login failed when connecting to SQL Server..."). I would like to know if the problem is in my application or in the way that we log in the web services from windows CE edition.

sw.AccPistola("user", "passs")
sw.PreAuthenticate = True
sw.UseDefaultCredentials = True 

Public Sub AccPistola(ByVal usuario As String, ByVal pass As String)
            Dim results() As Object = Me.Invoke("AccPistola", New Object() {usuario, pass})
            idioma = CType(results(0),String)

End Sub

Thanks for all and regards.