Hi.
I find bug in StockChart version 2013.2.716 (2013.2.626 is ok):

$("#stock-chart").kendoStockChart({
                dataSource: {
                    transport: {
                        read: {
                            url: "boeing-stock.json",
                            dataType: "json"
                        }
                    }
                },
                title: {
                    text: "The Boeing Company (NYSE:BA)"
                },
                dateField: "Date",
                series: [{
                    type: "line",
                    field: "Open",
                    name: "Open",
                }],
                navigator: {
                    series: {
                        type: "area",
                        field: "Close"
                    },
                    select: {
                        from: "2000/01/01",
                        to: "2010/01/01"
                    }
                },
                categoryAxis: { ... }
            });

[
    {
        "Date": "2000/01/03",
        "Open": 41.62,
        "High": 41.69,
        "Low": 39.81,
        "Close": 40.12,
        "Volume": 2632000
    },
    {
        "Date": "2000/01/04",
        "Open": 39.88,
        "High": 41.12,
        "Low": 39.75,
        "Close": 40.12,
        "Volume": 3584700
    },
    {
        "Date": "2000/01/05",
        "Open": null,
        "High": 43.31,
        "Low": 41.38,
        "Close": 42.62,
        "Volume": 7631700
    },
    {
        "Date": "2000/01/06",
        "Open": 42.25,
        "High": 43.44,
        "Low": 41.12,
        "Close": 43.06,
        "Volume": 4922200
    },
    {
        "Date": "2000/01/07",
        "Open": 43.88,
        "High": 44.88,
        "Low": 43.69,
        "Close": 44.12,
        "Volume": 6008300
    },
...
]

I set line series type and json data have null value.