There is a known problem with stale connections that are related to the KeepAlive property in the client proxy.  You might want to try turning off KeepAlives by modify the GetWebRequest method in the generated proxy class. In your generated proxy class, you could add the folowing code:

protected override System.Net.WebRequest GetWebRequest(Uri uri)
{
 System.Net.HttpWebRequest webRequest =
  (System.Net.HttpWebRequest) base.GetWebRequest(uri);
 webRequest.KeepAlive = false;
 return webRequest;
}

Hope that helps.