Image upload not working in server.. please help

Dear All,

   Please help me on this below, while uploading images in local the below code is working  fine. but when im move to server. its not working. please find the below simple code.

              string postFileName = filLogo.PostedFile.FileName;
                string upFileName = postFileName.Substring(postFileName.LastIndexOf("\\") + 1);
                if (postFileName != "")
                {          
                    postFileName = Request.PhysicalApplicationPath + "images\\userfiles\\" + upFileName;
                    filLogo.SaveAs(postFileName);
                }           

Any help will be much more appreciated.