C# .NET - Time out Exception when invoking GetResponse()

I create a WebRequest to post some HTML content to another web server. When I use normal text content, it works, but when I post HTML content I get a time out error when invoking GetResponse().

WebResponse response = request.GetResponse()

How can I figure out the issue? I tried adding an error handler for WebException but I could not catch the exception.

Request code :

byte[] byteArray = Encoding.UTF8.GetBytes(sPostData);

// Create a request using a URL that can receive a post. 
WebRequest request = WebRequest.Create(httpUri);
// Set the 'Timeout' property in Milliseconds.
//request.Timeout = 20000;
// Set the ContentType property of the WebRequest.
request.ContentType = contentType;
// Set the Method property of the request to POST.
request.Method = postMethod;
// Set the ContentLength property of the WebRequest.
request.ContentLength = byteArray.Length;
// Get the request stream.
using (Stream PostStream = request.GetRequestStream())
{
    PostStream.Write(byteArray, 0, byteArray.Length);
}
// Get the response.
using (WebResponse response = request.GetResponse())
{
    // Get the stream containing content returned by the server.
    using (Stream responseStream = response.GetResponseStream())
    {
        using (StreamReader reader = new StreamReader(responseStream))
        {
            string responseFromServer = reader.ReadToEnd();

            result = responseFromServer;
        }
    }
}