jQuery Grid Plugin - jqGrid

I'm working on a project where we had set up a prototype that used jqGrid 3.7.1 and local data to draw a series of grids. Sorting worked just fine on all of them.

Now we are creating the "real thing" and our jqGrid is getting its data from an XML String. Once this change was made, the grid stopped sorting. (Or so the original programmer tells me; my task is only to get one grid to sort.)

I have been "googling" like crazy to find out if there is something special I need to do to turn on sorting when using dataype: xmlstring, but I haven't seen anything or seen any bug reports related to using jqGrid this way.

Here is the declaration of the grid:

    $("#clientNotesTable").jqGrid({
        datatype: 'xmlstring',
        datastr: noteData,
        colNames: ['Date','Author','Type','Description','Task','Modified'],
        colModel: [
                    { name: 'created', index: 'created', width: 100, xmlmap: "Created", sorttype:'date'},
                    { name: 'authorName', index: 'authorName', width: 100, xmlmap: "AuthorName"},
                    { name: 'type', index: 'type', width: 100, xmlmap: "Type"},
                    { name: 'description', index: 'description', width: 350, xmlmap: "Description", formatter: descFormatter},
                    { name: 'state', index: 'state', width: 85, xmlmap: "State", formatter: taskFormatter, align:"center"},
                    { name: 'hiddenMod', index: 'hiddenMod', width: 0, xmlmap: "Modified", hidden:true}],
        xmlReader: {
            root: "notes",
            row: "note",
            repeatitems: false,
            id:"EntityId"
        },
        sortname: "Date",
        sortorder: 'asc',
        autowidth: true,
        altRows:true,
        altclass:'altRow'
    });

I would greatly appreciate any help I can get at this point, particularly as I'm supposed to have this finished by 9 am on Monday and it's after 5:00 pm on Friday.

Thanks!