下载提要时请求被取消

我在Azure上有一个worker角色。每两个小时，我从3个不同的附属公司下载产品。

第一次，当作业运行时，它工作完美。下次作业应该运行时，我从一个附属机构得到"请求被中止:请求被取消了"。其他两个工作完美。

不只是一次，每一次。我问过这家联营公司了，没有问题。所以一定是我的代码。我有这个下载json doc:

        using (var Client = new WebClient())
        {
            Client.Headers.Add("X-API-KEY", Key);
            Data = Client.DownloadString(URL);
        }

我错过了什么?

更新1:

我试过了:

        HttpWebRequest Req = (HttpWebRequest)WebRequest.Create(URL);
        Req.KeepAlive = false;
        Req.Headers.Add("X-API-KEY", Key);
        Req.Method = "GET";
        using (var Resp = Req.GetResponse())
        {
            using (var Reader = new StreamReader(Resp.GetResponseStream()))
            {
                Data = Reader.ReadToEnd();
            }
        }

同样的问题。

更新2

请求1

GET https://se.#####.com/1/stores.json HTTP/1.1
X-API-KEY: x.............N
Host: se.#####.com
Connection: Close

响应1

HTTP/1.1 200
Server: nginx
Date: Mon, 08 Jun 2015 14:56:39 GMT
Content-Type: application/json
Transfer-Encoding: chunked
Connection: close
Set-Cookie: ci_session=..............; expires=Mon, 08-Jun-2015 16:56:39 GMT; Max-Age=7200; path=/
e30
{"status":true,"data":[................]}
0

请求2

GET https://se.#####.com/1/stores.json HTTP/1.1
X-API-KEY: x.............N
Host: se.#####.com
Connection: Close

反应2

HTTP/1.1 200
Server: nginx
Date: Mon, 08 Jun 2015 15:06:29 GMT
Content-Type: application/json
Transfer-Encoding: chunked
Connection: close
Set-Cookie: ci_session=..................; expires=Mon, 08-Jun-2015 17:06:29 GMT; Max-Age=7200; path=/
e30
{"status":true,"data":[.....................]}
0

更新3

    [TestMethod]
    public void DownloadTest()
    {
          Test();
          Test();
          Test();
    }

    private static void Test()
    {
        const string merchantsUrl = "https://se.#####.com/1/stores.json";
        string Data;
        var Req = (HttpWebRequest)WebRequest.Create(merchantsUrl);
        Req.KeepAlive = false;
        Req.Headers.Add("X-API-KEY", ".....");
        Req.Method = "GET";
        using (var Resp = Req.GetResponse())
        {
            using (var Reader = new StreamReader(Resp.GetResponseStream()))
            {
                Data = Reader.ReadToEnd();
            }
        }
    }