jQuery Grid Plugin - jqGrid

Im having trouble with searching data. Everytime I type the search string, the navigation wont function (next, previous, etc). Sometimes the search box wont close. Here's the javascript i wrote

$(document).ready(function(){
  $("#list").jqGrid({
    url:'/administrators/groups/data',
    datatype: 'xml',
    mtype: 'POST',
    colNames:['ID','Name', 'Description'],
    colModel :[
      {name:'groupid', index:'groupid', width:20},
      {name:'groupname', index:'groupname'},
      {name:'groupdesc', index:'groupdesc'}],
    pager: jQuery('#pager'),
    autowidth: true,
    rowNum:10,
    rowList:[10,20,30],
    sortname: 'groupid',
    sortorder: "asc",
    viewrecords: true,
    ondblClickRow: function(rowid){
                    alert(rowid);
                },
    imgpath: '/themes/lightness/images',
    caption: 'Group List'
  }).navGrid('#pager',{edit:false,add:false,del:false});
  jQuery("#list").searchGrid(modal:true);
});

For the server side I use Codeigniter

    function xml()
    {
        $searchval = $_POST['searchString'];
        $searchfld = $_POST['searchField'];
        if($searchval <> '' && $searchfld <> ''):
            $where = "WHERE $searchfield LIKE '%$searchval%' ";
        endif;
        $page = $_POST['page'];
        $limit = $_POST['rows'];
        $sidx = $_POST['sidx'];
        $sord = $_POST['sord'];
        if(!$sidx) $sidx = 1;
        $sql     = "SELECT COUNT(*) AS count FROM bigp_web_group $where";
        $query     = $this->db->query($sql);
        $row     = $query->row_array();
        $count     = $row['COUNT'];
        if( $count > 0 ) {
                      $total_pages = ceil($count/$limit);
        } else {
                      $total_pages = 0;
        }
        if ($page > $total_pages) $page = $total_pages;
        $start = $limit * $page - $limit;
        if($start < 0) $start = 0;
        $SQL = "SELECT * FROM (SELECT r.*, ROWNUM as row_number FROM ( ";
        $SQL.= "SELECT * FROM bigp_web_group $where ORDER BY $sidx $sord) r ";
        $SQL.= "WHERE ROWNUM <= ".($limit*$page)." ) ";
        $SQL.= "WHERE ".($start+1)." <= row_number";
       
        $query = $this->db->query($SQL);
        $post = print_r($_POST, true);
        if ( stristr($_SERVER["HTTP_ACCEPT"],"application/xhtml+xml") ) {
                      header("Content-type: application/xhtml+xml;charset=utf-8");
        } else {
                  header("Content-type: text/xml;charset=utf-8");
        }
        echo "<?xml version='1.0' encoding='utf-8'?>";
        echo "<rows>";
        echo "<page>".$page."</page>";
        echo "<total>".$total_pages."</total>";
        echo "<records>".$count."</records>";
       
        foreach ($query->result_array() as $row) {
            echo "<row id='". $row['GROUPID']."'>";         
                        echo "<cell>".$row['GROUPID']."</cell>";
                        echo "<cell>".$row['GROUPNAME']."</cell>";
                        echo "<cell><![CDATA[".$post."]]></cell>";
            echo "</row>";
        }
        echo "</rows>";

    }