C# .NET client app not writing to stream for posting to website

I converted a program from java to c# using the JLCA in VS 2005.
I am trying to POST a string of values to a website and read the response returned.
It appears I am having a problem actually writing the string to the stream.
Here is the code:
----------------------------------------------------------
public virtual HttpResponse sendMessage()
{
      System.Text.StringBuilder responseBody = new System.Text.StringBuilder();
      HttpResponse httpResponse = new HttpResponse();
      System.IO.StreamReader buffer;
      char[] chunk = new char[2048];
      int bytesRead = 0;
      if (contentBody == null)
      {
            this.lastContentBody = "";
      }
      else
      {
                      this.lastContentBody = new System.Text.StringBuilder(contentBody).ToString();
      }

                      if (this.httpURLConn.Method.Equals("POST"))
      {

      try
      {
            System.IO.StreamWriter stOut = new System.IO.StreamWriter(httpURLConn.GetRequestStream(), System.Text.Encoding.Default);
            stOut.Write(contentBody);
            stOut.Close();

            buffer = new System.IO.StreamReader(new System.IO.StreamReader(httpURLConn.GetResponse().GetResponseStream(), System.Text.Encoding.Default).BaseStream, new System.IO.StreamReader(httpURLConn.GetResponse().GetResponseStream(), System.Text.Encoding.Default).CurrentEncoding);

            while ((bytesRead = buffer.Read(chunk, 0, chunk.Length)) != 0)
            {
                  responseBody.Append(chunk, 0, bytesRead);
            }

            HttpWebResponse respCode = (HttpWebResponse)httpURLConn.GetResponse();
            httpResponse.ResponseCode = (int)respCode.StatusCode;
      }

      catch (System.IO.IOException e)
      {
            //throw exception
      }
----------------------------------------------------------

Using VS debugging tools, I can see the "contentBody" string is a name/value set and is formatted correctly.
I receive and read the response correctly (verified by the server logs).

However, the reponse I am receiving is an error that indicates the string "contentBody"
is not getting written to the stream.

Any help is appreciated.

Thanks.

H.