jQuery Grid Plugin - jqGrid

Here's the JSON data, mimetype: application/json:

{"altRows": true, "rowList": [10, 25, 50, 100], "sortname": "id", "viewrecords": true, "autowidth": true, "forcefit": true, "shrinkToFit": true, "height": "auto", "caption": "My First Grid", "datatype": "json", "gridview": true, "colModel": [{"index": "shape", "editable": true, "name": "shape", "label": "shape"}], "sortorder": "asc", "url": "/mygrid/", "rowNum": 10, "pager": "#pager", "jsonReader": {"repeatitems": false}}

And here's the attempt to load it:

<script type="text/javascript">
jQuery("#mytable").jqGridImport({imptype:"json", impurl:"http://localhost:8000/mygrid/cfg"});
</script>

It results in just a gray thin bar, with no data grid. Firebug indicates that jqgrid is receiving the json data, but is doing nothing with it. No errors are produced.

Is the json data being output in a way which is unexepected? I'm using python's json_encode to generate the data, so I'd imagine it is correctly formatted.