Зависание формы при POST/get запросе

 Private Sub Btn_Conect_Click(sender As Object, e As EventArgs) Handles Btn_Conect.Click
        ' Анимация загрузки
        PictureBox1.Image = My.Resources.load
     
        ' Авторизация
        Dim postdata As String = "j_username=ЛОГИН&j_password=Пароль)"
        Dim tempCookies As New CookieContainer
        Dim encoding As New UTF8Encoding
        Dim bytedata As Byte() = encoding.GetBytes(postdata)
        Dim postReq As HttpWebRequest = DirectCast(WebRequest.Create("http://сайт"), HttpWebRequest)
 
        postReq.Method = "POST"
        postReq.KeepAlive = True
        postReq.CookieContainer = tempCookies
        postReq.ContentType = "application/x-www-form-urlencoded"
        postReq.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.90 Safari/537.36"
        postReq.ContentLength = bytedata.Length
        Dim postreqststream As Stream = postReq.GetRequestStream()
        postreqststream.Write(bytedata, 0, bytedata.Length)
        postreqststream.Close()
        Dim postresponse As HttpWebResponse
        postresponse = DirectCast(postReq.GetResponse(), HttpWebResponse)
        loginCookie = tempCookies
        postresponse.Close()
        postreqststream.Close()
 
        'По Get запросу получаем Json
        Dim GetReq As HttpWebRequest = DirectCast(WebRequest.Create(ЛИНК), HttpWebRequest)
        GetReq.CookieContainer = loginCookie
        Dim GetResponse As HttpWebResponse = DirectCast(GetReq.GetResponse(), HttpWebResponse)
        Dim reader = New StreamReader(GetResponse.GetResponseStream())
        JsonString = "{ ""GetTitr"": " & reader.ReadToEnd() & "}"
        GetResponse.Close()
        reader.Close()
End Sub