jQuery Grid Plugin - jqGrid

I am trying to load JSON data into a grid. I keep getting this error. My JSON data appears to be being correctly returned. Firebug says the error is in this line of the jqGrid code: if(g.cell)L=o[g.cell][C]||L}v=h===1?0:h;v=(v+d)%2==1?X:"";

Am I missing an option or something I should be setting?

I'm on a tight deadline and I can't get the grid to load any data at all. It says its loading and just hangs at this error. I've used jqGrid before with arrays but never with JSON data.

Any help is appreciated.

Version 3.8.1

Here's my code for calling the grid:

$('#cell_log_link').click(function(){
    $('#activate').hide();
    $('#contact_info').hide();
    $('#update_account').hide();
    $('#login').hide();
    $('#storage').hide();
    $('#validate').hide();
    $('#cell_log').show();
    $('#message').html("");
    $('#cell_log_grid').jqGrid({
    url:'XHR/get_cellLog?name='+$('input[name="UserName"]').val(),
    datatype: 'JSON',
    mtype: 'GET',
    colNames:['Cust Code','Designation','Study Number','Start Date','Status'],
    colModel :[
      {name:'Cust Code', index:'Cust Code', width:100},
      {name:'Designation', index:'Designation', width:175},
      {name:'Study Number', index:'Study Number', width:100, align:'left'},
      {name:'Start Date', index:'Start Date', width:75, align:'right'},
      {name:'Status', index:'Status', width:100},
    ],
     jsonReader : {
      root:"cell_log_data",
      page: "currpage",
      total: "totalpages",
      records: "numrecords"
   },
    altRows: true,
   // gridview: false,
    height: "100%",
    pager: '#pager',
    rowNum:50,
    rowList:[10,25,50],
    sortname: 'Start Date',
    sortorder: 'desc',
    subgrid: false,
    viewrecords: true,
    caption: 'Cell Log'
  });
});