jQuery Grid Plugin - jqGrid

My problem is when I use 'cn' and 'nc' in the search options property. It's appear 'undefined' in the combo and I want to use LIKE in the search. My version of jqgrid is 3.7.2 and jquery 1.4.2
My code works fine! I only had this problem.

my view:

<script language="javascript">
        jQuery(document).ready(function(){
          jQuery("#list").jqGrid({
            url:'@{getGridSignalData()}',
            datatype: 'xml',
            mtype: "POST",
            colNames:['Inv No', 'Name', 'Code', 'It is a Notification'],
            colModel :[
              {name:'invid', index:'invid', width:55, align:'center', hidden: true},
              {name:'name', index:'name', width:250, align:'center', editable:true, editoptions:{size:50}},
              {name:'code', index:'code', width:55, align:'center', editable:true, editoptions:{size:25}},
              {name:'notification', index:'notification', width:110, align:'center', editable:true, edittype:"checkbox", editoptions:{value:"Yes:No"}}
            ],
            pager: '#pager',
            rowNum:5,
            sortname: 'invid',
            sortorder: 'desc',
            width: "100%",
            height: "100%",
            viewrecords: true,
            caption: 'Signals',
            editurl:'@{submitGridSignalData()}'
          });
          jQuery("#list").jqGrid('navGrid','#pager', {del:false,add:false,edit:false,search:false});
          jQuery("#list").navButtonAdd('#pager', {caption: "", title: "Search", buttonicon: "ui-icon-search", position: "first",
              onClickButton: function() {
                  jQuery("#list").jqGrid('searchGrid', {drag: false, sopt:['eq','ne','lt','le','gt','ge','cn','nc'],
                      odata:['equal','not equal','less','less or equal','greater','greater or equal','contains','nor contains']});
              }
          });  
          ...

</script>

<table id="list"></table>
<div id="pager"></div>      

my controller:

    public static void getGridSignalData(Long id){
        List<Signal> signals = null;

        Map<String, String[]> in = params.all();
        Boolean search = Boolean.valueOf(in.get("_search")[0]);
        if(search){
            String searchField = in.get("searchField")[0];
            String searchOper = Utils.getSQLOperator(in.get("searchOper")[0]);
            String searchString = in.get("searchString")[0];
            String query = searchField+" "+searchOper+" ?";
            if(searchOper.equals("contains")){
                searchString = "%"+searchString+"%";
            }
            System.out.println("query: "+query+", searchString: "+searchString);
            signals = Signal.find(query, searchString).fetch();
        }

        else{
            signals = Signal.findAll();
        }

        Integer limit = Integer.valueOf(in.get("rows")[0]);
        Integer page = Integer.valueOf(in.get("page")[0]);        
        Integer records = signals.size();
        Integer total = records <= limit ? 1 : (records/limit)+1;        
        List<String[]> rows = new ArrayList<String[]>();
        int min = ((page-1)*limit);
        int max = (page*limit)-1;        
        for(int index=min; index < records && index <= max; index++){
            Signal signal = signals.get(index);
            rows.add(new String[] {
                signal.id.toString(), signal.name, signal.code.toString(), signal.notification ? "Yes" : "No"});
        }       
        String xml = Utils.dataToXml(page, total, records, rows);
        renderXml(xml);
    }   

thanks !!