$("#list1″).jqGrid({
              url: 'books.xml',
              datatype: "xml",
              colNames: ["Author", "Title", "Price", "Published Date"],
              colModel: [
           { name: "Author", index: "Author", width: 120, xmlmap: "ItemAttributes>Author" },
           { name: "Title", index: "Title", width: 180, xmlmap: "ItemAttributes>Title" },
           { name: "Price", index: "Manufacturer", width: 100, align: "right", xmlmap: "ItemAttributes>Price", sorttype: "float" },
           { name: "DatePub", index: "ProductGroup", width: 130, xmlmap: "ItemAttributes>DatePub", sorttype: "date" }],
              autowidth: true,
              height: 'auto',
              rowNum: 10,
              rowList: [10, 20, 30],
              viewrecords: true,
              loadonce: true,
              xmlReader: {
                  root: "Items",
                  row: "Item",
                  repeatitems: false,
                  id: "ASIN"
              },
              groupingView: { groupColumnShow: [false] },
              caption: "XML Mapping example"
          });

         $("#chngroup").change(function()
          {
              var vl = $(this).val();
              if (vl)
              {
                  if (vl == "clear")
                      $("#list1″).jqGrid('groupingRemove', true);
                      else
                      $("#list1″).jqGrid('groupingGroupBy', vl);
              }
          });

      });

</script>

  </head>
 
 <p>Sample</p>
 
<table id="list1″></table>
<div id="pager"></div>

<select id="chngroup">  
<option value="clear">-</option>
<option value="Author">Author</option>  
<option value="Title">Title</option>  
<option value="Price">Price</option>  
</select>

1. group by 'Title' column
2. clear grupping
3. column 'Title' does not become visible

jqGrid  3.8 / jQuery 1.4.2 / jQuery UI 1.8.2