jQuery Grid Plugin - jqGrid

i'm running jquery 1.3.2 and downloaded the jqGrid from the website with the package creator (full, and what i wanted specifically) but i get this error in both safari 4.0 and firefox 3.5.

safari full worded error:

TypeError: Result of expression '$.jgrid' [undefined] is not an object. jquery.jqgrid.js:9

here is my code:

$(function() {
  $('#po_order').jqGrid({
    url: '/ajax/jq_purchase_orders',
    datatype: 'json',
    colNames: ['Order Date', 'Status', 'Total'],
    colModel: [
      {name:'order_date', index:'order_date', width: 100, sortable:true},
      {name:'order_status', index:'order_status', width: 150, sortable:true},
      {name:'po_total', index:'po_total', width: 100, sortable:true}
    ],
    rowNum: 10,
    rowList: [10, 20, 40, 50],
    pager: $('#pager'),
    sortname: 'order_date',
    sortorder: 'desc',
    viewrecords: true,
    caption: 'Purchase Orders'
  });.navGrid('#pager', {edit:false, add:false, del:false});
});

pretty much right from the examples on the website.