Attached my source and xml.

From the example u can see that,only when i am using a custom item renderer this problem is happening.Otherwise it is working fine

Obviuosly I was not using the item renderer in the right way.Now i did it with AdvancedDataGridRendererProvider.But still i am getting the same problem.

This is the code :

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" width="100%" height="100%" xmlns:local="*">
    <mx:XML id='dp' source="data.xml"/>
    <mx:HierarchicalData id='hd' source="{dp.item}"/>
    <mx:AdvancedDataGrid x="174" y="126" width="390" height="381" id="adg1" sortableColumns="false"
        sortExpertMode="true" designViewDataType="tree" headerHeight="19" rowHeight="20"
        dataProvider="{hd}" editable="true">
        <mx:columns>
            <mx:AdvancedDataGridColumn dataField="@name" headerText="Item" width="197" editable="false"/>
            <mx:AdvancedDataGridColumn headerText="Display" id='display' dataField="@display" width="95" editable="false"/>
            <mx:AdvancedDataGridColumn headerText="Count" dataField="@count" width="55" editable="false"/>
        </mx:columns>
        <mx:rendererProviders>
            <mx:AdvancedDataGridRendererProvider column="{display}">
                <mx:renderer>
                    <mx:Component>
                        <mx:HBox horizontalAlign="center">
                        <mx:Script>
                            <![CDATA[
                                override public function set data(value:Object):void
                                {
                                        super.data = value;
                                        cb.selected=data.@display == 'yes'?true:false;
                                }   
                            ]]>
                        </mx:Script>
                            <mx:CheckBox id='cb' />
                        </mx:HBox>
                    </mx:Component>
                </mx:renderer>
            </mx:AdvancedDataGridRendererProvider>
        </mx:rendererProviders>
    </mx:AdvancedDataGrid>
    <mx:AdvancedDataGrid x="754" y="126" width="390" height="381" id="adg2" sortableColumns="false"
        sortExpertMode="true" designViewDataType="tree" headerHeight="19" rowHeight="20"
        dataProvider="{hd}" editable="true">
        <mx:columns>
            <mx:AdvancedDataGridColumn  dataField="@name" headerText="Item" width="197" editable="false"/>
            <mx:AdvancedDataGridColumn headerText="Display" dataField="@display" width="95" editable="false"/>
            <mx:AdvancedDataGridColumn headerText="Count" dataField="@count" width="55" editable="false"/>
        </mx:columns>
    </mx:AdvancedDataGrid>
</mx:Application>