[2005] Problem on request xML on https

I'm having a problem using the xml request and send on an https Website.

Well i'm using this code:

vb.net Code:

Private StrCertMsg As String
    Protected Function OnCertificateValidation(ByVal sender As Object, ByVal certificate As X509Certificate, ByVal chain As X509Chain, ByVal sslPolicyErrors As SslPolicyErrors) As Boolean
        StrCertMsg = "Server Certificate Issued To: " + certificate.Subject
        StrCertMsg = StrCertMsg + "Server Certificate Issued By: " + certificate.Issuer
        If Not (sslPolicyErrors) = sslPolicyErrors.None Then
            Return False
        Else
            Return True
        End If
    End Function
Public objRequest As HttpWebRequest
    Public Function get_lic(ByVal str As String) As System.Xml.XmlDocument
        Dim URL_BASE As String = "https://xml.website.com/xmlcenter/xmlquery.php"
        Dim xmlDoc As System.Xml.XmlDocument
        xmlDoc = New System.Xml.XmlDocument
        Dim result As String = ""
        Dim myWriter As StreamWriter
        Dim sXML = "<?xml version='1.0' encoding='UTF-8' ?><xmlcenter><auth><username>abcd</username><password>abcd123</password></auth>" & _
        "<xxxxx>" & _
        "<asse code=""" & str & """>" & _
        "</asse>" & _
        "</xxxx></xmlcenter>"
        ServicePointManager.CertificatePolicy = New MyCertificateValidation
        objRequest = WebRequest.Create(URL_BASE)
        objRequest.Method = "POST"
        Try
            myWriter = New StreamWriter(objRequest.GetRequestStream())
            myWriter.Write(sXML)
            myWriter.Flush()
            myWriter.Close()
        Catch e1 As Exception
            Response.Write(e1.Message)
        Finally
        End Try
        Dim objResponse As HttpWebResponse = objRequest.GetResponse()
        Dim sr As StreamReader
        sr = New StreamReader(objResponse.GetResponseStream())
        result = sr.ReadToEnd()
        sr.Close()
        xmlDoc.LoadXml(result)
        Return xmlDoc
    End Function

And i'm using this to:

vb.net Code:

Imports System.Security.Cryptography.X509Certificates
Public Class MyCertificateValidation
    Implements System.Net.ICertificatePolicy
    Public Function CheckValidationResult(ByVal srvPoint As ServicePoint, _
    ByVal cert As X509Certificate, ByVal request As WebRequest, ByVal problem As Integer) _
       As Boolean Implements ICertificatePolicy.CheckValidationResult
        Return True ' Accept all certificates
    End Function
End Class
Public Class RequestState
    Public request As WebRequest = Nothing
    Public requestDocument As String
End Class

This works. . . but sometimes it gives me a strange error. :| Is there anyway to do this without any marge to mistakes?