Why is file uploads through Silverlight 2 limited to .TXT files only?

I have a Silverlight 2 application that is sending a byte array to a Silverlight-enabled WCF service. However (if I don't try to load the .txt file) the service method is SaveFile()

never reached and I get the error: "The remote server returned an error: NotFound"

Am I missing something really obvious? Why can't I upload .doc files? Why only .txt?

UPDATE: I tried to attach a debugger for CLR exceptions, but it didn't help. I still don't see any errors other than 404. Here's my code:

in Page.xaml.cs:

OpenFileDialog dlg = new OpenFileDialog();

if (dlg.ShowDialog().Value)
{
  byte[] fileContent = new byte[dlg.File.Length];

  using (FileStream fs = dlg.File.OpenRead())
  {
    fs.Read(fileContent, 0, Convert.ToInt32(fs.Length));
    fs.Close();
  }

  Service1.Service1Client srv = new SL1.Service1.Service1Client();

  srv.SaveFileCompleted += (sender1, e1) =>
  {
    foo.Text = "Uploaded!";
  };

  srv.SaveFileAsync(dlg.File.Name, fileContent);
}

      

        
        
        
      

    

in Service1.svc.cs:

[OperationContract]
public string SaveFile(string fileName, byte[] fileContent)
{
  string ret = String.Empty;

  try
  {
    string target = @"c:\debug123\" + fileName;

    if (File.Exists(target))
    {
      File.Delete(target);
    }

    File.WriteAllBytes(target, fileContent);

    ret = "OK";
  }
  catch (Exception ex)
  {
    ret = ex.ToString();
  }

  return ret;
}

      

        
        
        
      

    

Does anyone see something wrong with this?