When you work with WPF application and try to export the Chart to png image format, if you call export in the MouseDobleClick appears an exception. 
This problem occurs if you use MouseDobleClick in Windows XP. 
See next code to reproduce the problem:
        public MainWindow()
        {
            InitializeComponent();
            InitializeChart();

        }
        private void InitializeChart()
        {
            Steema.TeeChart.WPF.Styles.Line line1 = new Steema.TeeChart.WPF.Styles.Line(tChart1.Chart);
            line1.FillSampleValues();
            tChart1.MouseDoubleClick += new MouseButtonEventHandler(tChart1_MouseDoubleClick);
        }
        void tChart1_MouseDoubleClick(object sender, MouseButtonEventArgs e)
        {
           tChart1.Export.Image.PNG.Save("C:\\Test.png"); 
        }