unable to edit data in jqgrid fetching data from database

$(document).ready(function() {
            $.ajax({
                type: "POST",
                contentType: "application/json",
                data: "{}",
                url: "MooseUpdate.aspx/getEditMoose",
                dataType: "json",
                shrinkToFit: false,
                success: function(data) {
                    data = data.d;
                    $("#list").jqGrid({
                        datatype: "local",
                        colNames: ['Event ID', 'SBCUID', 'Event Description', 'Calendar Date', 'Availablity'],
                        colModel: [{ name: 'EventID', index: 'EventID', width: 65, stype: 'text', sortable: true, sorttype: 'int', editable: false, editrules: { integer: true} },
                                   { name: 'SBCUID', index: 'SBCUID', width: 75, stype: 'text', sortable: true, editable: false },
                                   { name: 'EventDesc', index: 'EventDesc', width: 140, stype: 'text', sortable: true, formoptions: { rowpos: 1, colpos: 1 }, editrules: { integer: false }, align: 'center',
                                    editable: true,
                                    edittype: 'select',
                                    formatter: 'select',
                                    editoptions: { value: "Office:Office;unavailable:unavailable" }
                                    },            
                                  { name: 'CalDate', index: 'CalDate', width: 150, stype: 'text', sortable: true, editable: false },
                                  { name: 'avbl', index: 'avbl', width: 150, stype: 'text', sortable: true, editable: true, formoptions: { rowpos: 2, colpos: 1 }, editrules: { string: true} }
                                  ],
                        data: JSON.parse(data),
                        rowNum: 60,
                        loadonce: false,
                        cmTemplate: { sortable: false },
                        rowlist: [10, 20, 30],
                        emptyrecords: "Nothing to display",
                        pager: '#pager',
                        viewrecords: true,
                        gridview: true,
                        sortorder: 'asc',
                        toppager: true,
                        cloneToTop: true,
                        altrows: true,
                        autowidth: false,
                        hoverrows: true,
                        width: 700,
                        caseSensitive: false,
                        ignoreCase: true,
                        enabletooltips: true,
                        height: 400,
                        jsonReader: {
                            repeatitems: true
                        },
                        sortname: 'EventID',
                        toolbar: [true, "top"],
                        rownumbers: true,
                        caption: "Moose Update",
                        editurl: 'MooseUpdate.aspx/UpdateMoose',
                        'cellEdit': true
                    })