jQuery Grid Plugin - jqGrid

I am running jquery 1.3.2 and jqgrid 3.6.4 via FF 3.6 and seem to be seeing consistent handling of sub-objects. In the following example, the data is properly loaded via the addJSONData, but the sub-object grid columns are not being properly updated in the subsequent calls to setRowData and addRowData. Any suggestions?

    jQuery("#list4").jqGrid({
        jsonReader: { repeatitems : false, id: "0" },
        datatype: "json",
        height: 250,
        colNames:['Inv No',
            'Date',
            'Client',
            'Amount',
            'Tax',
            'Total',
            'Notes'],
        colModel:[ {name:'id',index:'id', width:60, sorttype:"int"},
            {name:'invdate',index:'invdate', width:90, sorttype:"date"},
            {name:'name',index:'name', width:100},
            {name:'sub.amount',index:'sub.amount', width:80, align:"right",sorttype:"float"},
            {name:'sub.tax',index:'sub.tax', width:80, align:"right",sorttype:"float"},
            {name:'sub.total',index:'sub.total', width:80,align:"right",sorttype:"float"},
            {name:'note',index:'note', width:150, sortable:false} ],
        caption: "Manipulating Array Data"
    });

    jQuery('#list4')[0].addJSONData({"page":"1","total":2,"records":"13","rows":[{"id":"13","invdate":"2007-10-06","name":"Client 3","sub":{"amount":"1000.00","tax":"0.00","total":"1000.00"},"note":null},{"id":"12","invdate":"2007-10-06","name":"Client 2","sub":{"amount":"700.00","tax":"140.00","total":"840.00"},"note":null},{"id":"11","invdate":"2007-10-06","name":"Client 1","sub":{"amount":"600.00","tax":"120.00","total":"720.00"},"note":null},{"id":"10","invdate":"2007-10-06","name":"Client 2","sub":{"amount":"100.00","tax":"20.00","total":"120.00"},"note":null},{"id":"9","invdate":"2007-10-06","name":"Client 1","sub":{"amount":"200.00","tax":"40.00","total":"240.00"},"note":null},{"id":"8","invdate":"2007-10-06","name":"Client 3","sub":{"amount":"200.00","tax":"0.00","total":"200.00"},"note":null},{"id":"7","invdate":"2007-10-05","name":"Client 2","sub":{"amount":"120.00","tax":"12.00","total":"134.00"},"note":null},{"id":"6","invdate":"2007-10-05","name":"Client 1","sub":{"amount":"50.00","tax":"10.00","total":"60.00"},"note":null},{"id":"5","invdate":"2007-10-05","name":"Client 3","sub":{"amount":"100.00","tax":"0.00","total":"100.00"},"note":"no tax"},{"id":"4","invdate":"2007-10-04","name":"Client 3","sub":{"amount":"150.00","tax":"0.00","total":"150.00"},"note":"no tax"}]});
    jQuery("#list4").jqGrid('setRowData',13,{"id":"13","invdate":"2010-03-02","name":"Modified","note":"setRowData","sub":{"amount":"333.00","tax":"222.00","total":"444.00"}});
    jQuery("#list4").jqGrid('addRowData',15,{"id":"15","invdate":"2010-03-02","name":"Added","note":"addRowData","sub":{"amount":"444.00","tax":"333.00","total":"555.00"}});