jQuery Grid Plugin - jqGrid

I have a grid on which I need to populate the edit form with data fetched from the server for one particular element.  The grid constructor is:

jQuery("#dataList").jqGrid({
        url:'/input/getcamp?format=json',
        datatype: "json",
        colNames:['Id','Name','Brand','Property','Attributes'],
        colModel:[
            {name:'id',index:'id', width:0,editable:false,hidden:true},
            {name:'cName',index:'cName',editable:true,sortable:true,editrules:{required:true}},
            {name:'bName',index:'bName',sortable:true,editable:true,edittype:"select",editoptions:{value:selBrand}},
            {name:'pName',index:'pName',sortable:true,editable:true,edittype:"select",editoptions:{value:selProperty}},
            {name:'attribs',index:'attribs',hidden:true,editable:true,edittype:'custom',editoptions:{custom_element:_setCheckGroup,custom_value:_getCheckGroup},editrules:{edithidden:true}}
        ],
        rowNum:10,
        rowList:[10,20,30,40,50],
        pager: '#dataListPager',
        sortname: 'id',
        viewrecords: true,
        sortorder: "desc",
        caption:"Campaign Maintenance",
        autowidth:true,
        height:300,
        scroll:true,
        loadComplete:function(){gridOnLoad();},
        onSelectRow:function(){showEditRowButton();}
    });

The custom functions are:

//set up the attributes edit element in campaign edit
function _setCheckGroup(value, options) {
    var cId = $("#dataList").jqGrid('getGridParam','selrow');
    var t = $("#dataList").jqGrid();
    var xhtml = '';
    var ele = document.createElement('rbAttribs');
    $.ajax({url:'/input/getattrib?format=json&cId=' + cId,
        success:function(response){
            if(response.success) {
                for (var x in response.data.allAttribs) {
                    xhtml += '<input type="checkbox" name="attribs" value="' + x + '"';
                    if (response.data.thisAttribs[x]) {
                        xhtml += ' checked';
                    }
                    xhtml += ' />' + response.data.allAttribs[x]
                }
                $(ele).html(xhtml);
            } else {
                simplePopupMessage({title:"Oops!",message:response.msg,class:'negative'});
                return false;
            }
        },
        cache:false,
        async:false,
        dataType:'json'
    });
    return ele;
}

//return value of edited attributes element from campaign edit
function _getCheckGroup(ele) {
    var ret = '';
    $(ele + ':checked').each(function(){
        ret += $(this).val() + '|';
    });
    return ret.replace(/\|$/,'');
}

recreateForm is set true in both the edit and add options for the forms

Now this all works fine the first time I edit a row, but for the second and subsequent edits, the _setCheckGroup() function is never called and therefore the contents of the check boxes is not updated from the server.  How can I get the grid/form to call _setCheckGroup() every time I edit a row?