I have a GridPanel with summary feature enabled. All columns defined like so:
xtype: 'gridcolumn', //or some other type
dataIndex: 'blah', //some dataIndex
text: 'Blah-blah-blah', //some header text
flex: 1, //some other values also, but every column has its flex option
summaryType: 'sum' //or count, some columns has no summary feature enabled
The GridView displays data as expected, but summary row expands some columns and all following columns are shifted right. Here is an example (I colored all td tags of summary row tr tag, so you can easily see the bug. All columns are not hidden. Chrome 27): bug.jpg
Here is a demo jsfiddle (in editor it looks good, but in full screen you could see bugs with column size).