I have a simple gridpanel - with a summary feature - I have a componentcolumn - which whorked great, until I dropped the summary in - now, the componentColumn throws: " Unable to get value of the property 'rowIndex': object is null or undefined" - works fine without adding the simple summary below - but as soon as I add the summary - the error occurs?

Here is the column 
 <ext:ComponentColumn ID="ComponentColumn1" runat="server" Editor="true" DataIndex="Quantity"
                                            Width="45" Align="Right" Text="Qty">
                                            <Component>
                                                <ext:NumberField ID="NumberField1" MinValue="1" AllowDecimals="false" AllowBlank="false"
                                                    Width="45" Align="Right" runat="server">
                                                    <Listeners>
                                                        <Blur Handler="Ext.getCmp('GridPanel2').store.commitChanges();" />
                                                        <Focus Handler="Ext.getCmp('GridPanel2').store.commitChanges();" />
                                                    </Listeners>
                                                </ext:NumberField>
                                            </Component>
                                        </ext:ComponentColumn>
Here is the feature:
<Features>
                                    <ext:Summary runat="server" ID="Summary1">
                                    </ext:Summary>
                                </Features>