Unauthorised access when trying to view a report in ReportViewer control

Hi All,
I'm trying to view a Reporting Services report via my web application, however I keep getting a 401 Unauthorised error message. Here's what I have in my code:
protected void Page_Load(object sender, EventArgs e)
    {
        ReportViewer1.ProcessingMode = ProcessingMode.Remote;

        ReportViewer1.ServerReport.ReportServerCredentials = new ReportServerNetworkCredentials();

        string reportServerLocation = ConfigurationManager.AppSettings["REPORT_SERVER"];
        ReportViewer1.ServerReport.ReportServerUrl = new Uri("myURL");
        ReportViewer1.ServerReport.ReportPath = "myPath";
        ReportViewer1.ShowParameterPrompts = false;
  & ...