code that downloads images - for stackoverflow question: http://stackoverflow.com/questions/14158069/the-request-was-aborted-could-not-create-ssl-tls-secure-channel-in-windows-8-me

gistfile1.cs

        async private void Download_Click_1(object sender, RoutedEventArgs e)
        {
            string[] files =
            {
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg",
                "https://si0.twimg.com/profile_images/523560950/discount_1__bigger.jpg"
            };

            List<Task<Byte[]>> tasks = new List<Task<Byte[]>>();
            for (int idx = 0; idx < files.Count(); idx++)
            {
                var file = files[idx];

                var taskStart = DownloadImageData(new Uri(file), null);
                tasks.Add(taskStart);

                if (((idx > 0) && (idx % 5 == 0)) || (idx == files.Count() - 1))
                {
                    await Task.WhenAll(tasks);
                    tasks.Clear();
                }
            }
        }

        private async Task<Byte[]> DownloadImageData(Uri url, Object userState)
        {
            Byte[] contentBytes = null;

            using (HttpClientHandler _handler = new HttpClientHandler())
            {
                _handler.AllowAutoRedirect = true;
                _handler.MaxAutomaticRedirections = 4;

                using (HttpClient httpClient = new HttpClient(_handler))
                {
                    httpClient.DefaultRequestHeaders.ExpectContinue = false;
                    httpClient.DefaultRequestHeaders.Add("Keep-Alive", "false");

                    try
                    {
                        // Exception IS THROWN AT LINE BELOW 
                        contentBytes = await httpClient.GetByteArrayAsync(url.OriginalString);
                    }
                    catch (Exception ex)
                    {
                        System.Diagnostics.Debug.WriteLine("Download Failed :" + ex.Message);
                        throw ex;
                    }
                }

                _handler.Dispose();
            }

            return contentBytes;
        }