jQuery Grid Plugin - jqGrid

Hi,

i am using your awesome plugin to show my data in a modal window (UI jquery plugin)

the grid loads my data pretty fine in the first page  load (and in the page reloads), but in the other cases (simple java script calls from within the application buttons) it loads always the same data,

it seems to require a certain data reload, i tried with the method GridUnload but when i made some traces inside the method's code it looks like it's not recognizing my grid ( it stops at this line "if ( !this.grid ) {alert("my custom debug trace :: unable to unload grid"); return;}")

My code is the following

       jQuery(document).ready(function(){
        $("#myWindow").dialog({
            bgiframe: true,
            autoOpen: false,
            autowidth:true,
            width: 800,
            height: 280,
            modal: true,
             resizeStop: function() {
              
                //jQuery("#myGrid").width = $('#myWindow').dialog('option', 'width')- 20;
                //jQuery("#myGrid").height =  $('#myWindow').dialog('option', 'height')- 50;
                //$("#myGrid").width = $('#myWindow').dialog('option', 'width')- 20;
                //mygrid.height =  $('#myWindow').dialog('option', 'height')- 50;
            }
            ,open: function(){                                                            
                        $("#myGrid").GridUnload();
                        $("#myGrid").jqGrid({
                        //TODO transform to full path
                        url:"mydata.php",
                        datatype: 'json',
                        mtype: 'POST',
                        colNames:['Date','Modification','Application','Qui','Valeur','Commentaires'],
                        colModel :[
                           {name:'id', width:80,stype:'label'},
                           {name:'id', width:80,stype:'label'},
                          {name:'v', index:'v',width:80,stype:'label'},
                          {name:'m', index:'m', width:80,stype:'label'},
                          {name:'projet', index:'projet', width:80 ,stype:'label'},
                          {name:'xfn', index:'xfn', width:80 ,stype:'label'},
                        ],
                        pager: jQuery('#pager2'),
                        rowNum:10,
                        rowList:[5,10,15],
                        sortname: 'id',
                        sortorder: "asc",
                        viewrecords: true,
                        caption: 'Caption goes here',
                        width:770
                      })
     
            }
        });
        $('#myWindow').dialog('open');
        });

Thanks a lot !