Not able to upload when runned on web server

I need to upload files to the web server using FtpWebRequest. I have the codes below which worked just fine when i run it in my localhost but when i run it on the web server im getting errors "File not found". I believe it's a permission/security issue over here. Could someone help me out here?
 Thanks in advance

Default.aspx.csusing System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net;
using System.IO;

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventAr ...