File Upload Issue #23

Hi All,
Can Any one pls check this issue....
I am getting "Authentication Failed Error" when uploading file. But i can sucessfully getting the Metadata of files & folders. & and i can create folder.. Only issue in File Upload..
here is my code..

//_Code_********//

StreamResourceInfo sr = Application.GetResourceStream(new Uri("Background.png", UriKind.RelativeOrAbsolute));
byte[] databytes = new byte[sr.Stream.Length];
sr.Stream.Read(databytes, 0, databytes.Length);
dc.UploadFileAsync(@"/MyFolder/", "Background.png", databytes, new Action(Result));