原因：
Turns out my problem was in the definition of Ext.grid.ColumnModel. My autoexpand column which I selected in the definition of the grid was "name":
autoExpandColumn:"name",
this means that I needed a corresponding definition in the ColumnModel with an "ID". I thought the ID was referring to the XML record, but it's referring to an ID in the column Model:
{id: 'name', header: "Project Name", width:200, sortable:true, dataIndex:"name"}
if you don't have the ID it will fail to compare, return -1 for the call at ext-all-debug.js:31525
解决办法：
给autoExpandColumn对应的属性在ColumnModel中的定义加个id属性，如下：
{[b][color=red]id:'name'[/color][/b],header: "name",width: 75, sortable: true, dataIndex: 'name'},
