A "never seen before" javascript error (Access to property denied" code: "1010)

Question

I was testing my jqgrid and when I was attempting to add details through jqgrid's modal window I came across the following error in my firebug console.

Access to property denied" code: "1010
checkValues("2010-04-20", 5, table#list.ui-jqgrid-btable)grid.common.js (line 441)
postIt()grid.formedit.js (line 794)
anonymous(Object originalEvent=Event click type=click)grid.formedit.js (line 463)
anonymous(Object originalEvent=Event click type=click)jquery-1....2.min.js (line 19)
anonymous()jquery-1....2.min.js (line 19)

Where do I start in solving this issue?

Below is my jqgrid code

<div class="grid">      
    <!-- the grid definition in html is a table tag with class 'scroll' -->
    <table id="list" class="scroll" cellpadding="0" cellspacing="0"></table>
    <!-- pager definition. class scroll tels that we want to use the same theme as grid -->
    <div id="pager" class="scroll" style="text-align:center;"></div>                
</div>

<script type="text/javascript">
    $(document).ready(function(){
        $("#list").jqGrid({
            width: 800,
            height: 240,
            autowidth: false,
            rownumbers: true,
            rownumWidth: 40,
            url:'<?php echo $this->baseUrl() ?>/expensedetails/list',
            datatype: 'json',
            mtype: 'POST',
            colNames:['ID','TYPEID','Description','Amount','Date'],
            colModel :[                
                {name:'id', index:'id',
                    width:10,
                    hidden:true
                },                                  
                {name:'expense_details_linktype', index:'expense_details_linktype',
                    width:10,
                    hidden:true
                },
                {name:'expense_details_desc', index:'expense_details_desc',
                    sortable:true,
                    editable:true,
                    edittype:"select",
                    editoptions:{value:"<?php echo $values?>"},
                    editrules:{required:true},
                    searchoptions:{sopt:['eq','ne','bw','bn','in','ni','ew','en','cn','nc']}
                },
                {name:'expense_details_amount', index:'expense_details_amount',
                    width:30,
                    sortable:true,
                    editable:true,
                    editoptions:{size:10},
                    editrules:{number:true,required:true}
                },
                {name:'expense_details_date', index:'expense_details_date',
                    width:40,
                    sortable:true,
                    editable:true,                  
                    editrules:{date:true,required:true},
                    searchoptions:{sopt:['eq','ne','lt','le','gt','ge']},
                    editoptions: {
                        size: 10, maxlengh: 10,
                        dataInit: function(el) {
                          $(el).datepicker({dateFormat: 'yy-mm-dd'})
                        },
                        defaultValue: function(){ 
                            var currentTime = new Date(); 
                            var month = parseInt(currentTime.getMonth() + 1); 
                            month = month <= 9 ? "0"+month : month; 
                            var day = currentTime.getDate(); 
                            day = day <= 9 ? "0"+day : day; 
                            var year = currentTime.getFullYear(); 
                            return year+"-"+month + "-"+day; 
                          } 
                      }                         
                }
            ],
            pager: $('#pager'),
            rowNum:10,            
            rowList:[10,20,30],
            sortname: 'expense_details_date',
            sortorder: "desc",
            viewrecords: true,
            viewsortcols: [true,'horizontal',true],
            gridview: false,
            hidegrid: false,
            editurl:"<?php echo $this->baseUrl() ?>/expensedetails/edit",
            caption: 'Enter or Adjust Your Expenses',
            forceFit : true
        });

        $("#list").jqGrid('navGrid','#pager',               
                {add:true,addtext:'Add',edit:true,edittext:'Edit',del:true,deltext:'Delete',view:true,viewtext:'View',search:true,searchtext:'Search',refresh:true,refreshtext:'Refresh'},              
                {url:'<?php echo $this->baseUrl() ?>/expensedetails/edit',closeAfterEdit:'true'},
                {url:'<?php echo $this->baseUrl() ?>/expensedetails/add',closeAfterAdd:'true'},                                                         
                {url:'<?php echo $this->baseUrl() ?>/expensedetails/delete',closeAfterAdd:'true'}
            );
        $("#list").jqGrid('searchGrid', {multipleSearch:true} );    
    });

</script>