c# smartdevice - HTTPWEBREQUEST GET vs POST InvalidOperationException

In the code below, DoGet is working very stable. But DoPost throws an uncatcheable InvalidOperationException randomly. I am lost. Any pointers will be of immense help.

/*
    Environment
    -------------
    * NET CF 2.0
    * WM 5.0(USA Mobile Pocket PC Emulator)
    * Windows XP Professional SP2
    * VS 2008
*/

/*
    The exception
    ------------------
   at System.Net.HttpWebRequest.set_ContentLength(Int64 value)
   at System.Net.HttpWebRequest.BufferConnectStream.WritingSucceeds()
   at System.Net.HttpWriteStream.doClose()
   at System.Net.HttpWriteStream.Finalize()
*/

public static string DoPost(string url)
{
    // initialize from variables
    string responseString = string.Empty;
    ASCIIEncoding encoding = new ASCIIEncoding();
    HttpWebResponse response;
    byte[] data = encoding.GetBytes("dummy");
    StreamReader reader;
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);

    //do the processing
    SetRequestProperties(request, "POST"); // SETTING METHOD TO POST HERE
    request.GetRequestStream().Write(data, 0, data.Length);
    request.GetRequestStream().Close();
    response = (Htt开发者_运维知识库pWebResponse)request.GetResponse();
    reader = new StreamReader(response.GetResponseStream());
    responseString = reader.ReadToEnd();

    //clean up
    response.Close();
    response.GetResponseStream().Close();
    response.GetResponseStream().Dispose();
    reader.Close();
    reader.Dispose();
    reader = null;
    response = null;
    request = null;
    encoding = null;

    //return
    MessageBox.Show("POST SUCCESS");
    return responseString;

}   

public static string DoGet(string url)
{
    // initialize from variables
    string responseString = string.Empty;
    ASCIIEncoding encoding = new ASCIIEncoding();
    HttpWebResponse response;
    byte[] data = encoding.GetBytes("dummy");
    StreamReader reader;
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);

    //do the processing
    SetRequestProperties(request, "GET");  // SETTING METHOD TO GET HERE
    response = (HttpWebResponse)request.GetResponse();
    reader = new StreamReader(response.GetResponseStream());
    responseString = reader.ReadToEnd();

    //clean up
    response.Close();
    response.GetResponseStream().Close();
    response.GetResponseStream().Dispose();
    reader.Close();
    reader.Dispose();
    reader = null;
    response = null;
    request = null;
    encoding = null;

    //return
    MessageBox.Show("GET SUCCESS"); 
    return responseString;

}

private static void SetRequestProperties(HttpWebRequest request, string s)
{
    request.Method = s;
    request.AllowWriteStreamBuffering = true;
    request.KeepAlive = false;
    request.ContentType = "application/x-www-form-urlencoded";
    request.SendChunked = false;
    request.Credentials = CredentialCache.DefaultCredentials;
    request.UserAgent = "my mobile user agent";
    request.Timeout = 60000;
    request.ProtocolVersion = new System.Version("1.1");
}

is this related to the following linklink text?