When i pu autocomplete code my jquery not working why that

here is my code

<link href="/Content/jquery-ui-1.8.2.custom.css" rel="stylesheet" type="text/css" />
<link href="/Content/ui.jqgrid.css" rel="stylesheet" type="text/css" />
<link href="/Content/ui.multiselect.css" rel="stylesheet" type="text/css" />
<script src="/Scripts/jquery-1.5.1.min.js" type="text/javascript"></script>
<script src="/Scripts/grid.locale-en.js" type="text/javascript"></script>
<script src="/Scripts/jquery.jqGrid.min.js" type="text/javascript"></script>

<script  src="@Url.Content("~/Scripts/jquery.ui.autocomplete.js")" type="text/javascript"></script>
<script  src="@Url.Content("~/Scripts/jquery.ui.core.js")" type="text/javascript"></script>
<script  src="@Url.Content("~/Scripts/jquery.ui.datepicker.js")" type="text/javascript"></script>

<link href="@Url.Content("~/Content/jquery.ui.datepicker.css")" rel="stylesheet" type="text/css" />
<link href="@Url.Content("~/Content/jquery-ui-1.8.18.custom.css")" rel="stylesheet" type="text/css" />
<link href="@Url.Content("~/Content/jquery.ui.autocomplete.css")" rel="stylesheet" type="text/css" />

<script type="text/javascript">


    $(document).ready(function () {

         $("#GivenComment").autocomplete({
            source: function (request, response) {
                $.ajax({
                    type: "POST",
                    contentType: "application/json; charset=utf-8",
                    url: "/Comment/SearchAutoComplete",
                    data: "{'term':'" + request.term + "'}",
                    dataType: "json",
                    async: true,
                    success: function (data) {
                        response(data.d);
                    },

                    error: function (result) {
                        alert("Due to unexpected errors we were unable to load data");

                    }
                });

            },

            minLength: 2

        });