With this xaml:

	<ig:XamGrid ItemsSource="{Binding Items}" AutoGenerateColumns="False" ColumnWidth="*" BorderThickness="0" HorizontalAlignment="Stretch" Background="White" Foreground="{StaticResource BodyTextColorBrush}" CellStyle="{StaticResource AlternatingCellStyle}">

		<ig:XamGrid.Columns>
			<ig:TextColumn Width="120" Key="Date" ValueConverter="{StaticResource DateConverter}" HeaderStyle="{StaticResource HeaderCellStyle}" IsSummable="False" AllowToolTips="Always"/>
			<ig:TextColumn Width="180" Key="Reference" HeaderStyle="{StaticResource HeaderCellStyle}" IsSummable="False" AllowToolTips="Always"/>
			<ig:TextColumn Width="3*" Key="CategoryName" HeaderText="Category" HeaderStyle="{StaticResource HeaderCellStyle}" IsSummable="False" AllowToolTips="Always"/>
			<ig:TextColumn Width="2*" Key="AnalysisCodesText" HeaderText="Analysis" HeaderStyle="{StaticResource HeaderCellStyle}" IsSummable="False" AllowToolTips="Always"/>
			<ig:TextColumn Width="80" Key="DebitValue" HeaderText="Debit" ValueConverter="{StaticResource StringConverter}" HeaderStyle="{StaticResource HeaderCellStyle}" CellStyle="{StaticResource RightCellStyle}" IsSummable="False" AllowToolTips="Always">
				<ig:TextColumn.SummaryColumnSettings>
					<ig:SummaryColumnSettings>
						<ig:SummaryColumnSettings.SummaryOperands>
							<Controls:DebitValueSummariserOperand/>
						</ig:SummaryColumnSettings.SummaryOperands>
					</ig:SummaryColumnSettings>
				</ig:TextColumn.SummaryColumnSettings>
			</ig:TextColumn>
			<ig:TextColumn Width="80" Key="CreditValue" HeaderText="Credit" ValueConverter="{StaticResource StringConverter}" HeaderStyle="{StaticResource HeaderCellStyle}" CellStyle="{StaticResource RightCellStyle}" IsSummable="False" AllowToolTips="Always">
				<ig:TextColumn.SummaryColumnSettings>
					<ig:SummaryColumnSettings>
						<ig:SummaryColumnSettings.SummaryOperands>
							<Controls:CreditValueSummariserOperand/>
						</ig:SummaryColumnSettings.SummaryOperands>
					</ig:SummaryColumnSettings>
				</ig:TextColumn.SummaryColumnSettings>
			</ig:TextColumn>
			<ig:ImageColumn Key="EditImage" HorizontalContentAlignment="Center" Width="20" HeaderText=" " HeaderStyle="{StaticResource HeaderCellStyle}" IsSummable="False" AllowToolTips="Always"/>
			<ig:ImageColumn Key="InvoiceImage" HorizontalContentAlignment="Center" Width="20" HeaderText=" " HeaderStyle="{StaticResource HeaderCellStyle}" IsSummable="False" AllowToolTips="Always"/>
		</ig:XamGrid.Columns>
		<ig:XamGrid.DeferredScrollingSettings>
			...
		</ig:XamGrid.DeferredScrollingSettings>
		<ig:XamGrid.SummaryRowSettings>
			<ig:SummaryRowSettings AllowSummaryRow="Bottom" Style="{StaticResource EmptySummaryCellStyle}"/>
		</ig:XamGrid.SummaryRowSettings>
	</ig:XamGrid>
	

Restoring the properties doesn't work.  PersistenceLoaded only has one PropertyPersistenceExceptionDetails:

Exception: "A column has been added with an Empty key. All columns must have a unique key."
PropertyInfo: {Infragistics.Controls.Grids.ColumnLayoutCollection ColumnLayouts}
PropertyPath "ColumnLayouts"

Is it obvious what I'm getting wrong?