jQuery Grid Plugin - jqGrid

Hi there, I have run into an issue that I can't seem to find a solution for on other forum posts. I have a master grid, with sub grids configured everytime you click on the + symbol next to a row. What I'm finding is that when i click the + without moving my mouse the subgrid renders fine, as soon as i move my mouse it disappears and won't come back unless i collapse and expand again.

I have found posts with users having similar issues and have tried downloading the latest files from github, but this still doesn't work for me. I am using the latest version of IE 8. Here is my code:

$("#contractors").jqGrid({

        url:'contractor_data.aspx?call=' + $("#<%= lblContractorCompany.ClientID %>").text(),

        datatype: 'json',

        mtype: 'GET',

        colNames:['ID','Full Name'],

        colModel:[

            {name:'ID',index:'ID', width:100,hidden:true},

            {name:'FullName',index:'FullName', width:55}            

        ],

        pager: "#contractorsPager",

        rowNum:-1,

        autowidth:true,

        height:"100%",

        sortname: 'ID',

        sortorder: "desc",

        viewrecords: true,

        caption: 'Contractors',

        subGrid: true,

        subGridRowExpanded: function(subgrid_id, row_id) {

            // we pass two parameters

            // subgrid_id is a id of the div tag created within a table

            // the row_id is the id of the row

            // If we want to pass additional parameters to the url we can use

            // the method getRowData(row_id) - which returns associative array in type name-value

            // here we can easy construct the following

            var subgrid_table_id;

            subgrid_table_id = subgrid_id+"_t";

            $("#"+subgrid_id).html("<table id='"+subgrid_table_id+"' class='scroll'></table>");

            $("#"+subgrid_table_id).jqGrid({

              url:"contractor_data.aspx?sub=true&fullname="+$("#contractors").getRowData(row_id).FullName + "&complete=" + $("#cbComplete").attr("checked") + "&verified=" + $("#cbVerified").attr("checked"),

              datatype: "json",

              colNames: ['ID','Customer','Full Name','Start Time','End Time','Project Name'],

              colModel: [

                {name:"ID",index:"ID",width:80},

                {name:"Customer",index:"Customer",width:130},

                {name:"FullName",index:"FullName",width:80,key:true},

                {name:"StartTime",index:"StartTime",width:80},           

                {name:"EndTime",index:"EndTime",width:100},

                {name:"ProjectName",index:"ProjectName",width:100}

              ],

              rowNum:-1,

              autowidth:true,

              height: "100%",

              rowNum:20,

              sortname: 'ID',

              sortorder: "desc"

            });

        }

    });

    $("#contractors").jqGrid('navGrid','#contractorsPager',{search:false,edit:false,add:false,del:false});