I'm trying to use radio buttons to change the data in a WebDataGrid (Ver.=11.1.20111.2020). The data initially loads up just fine, but when the radio button is clicked I get the following error:

Server Error in '/Web' Application.

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Object reference not set to an instance of an object.

[NullReferenceException: Object reference not set to an instance of an object.]
   Infragistics.Web.UI.GridControls.SummaryRow.GetSummaryValue(GridField field, Summary summary, ColumnSummaryInfo colSumInfo, SummaryRowSetting sumRowSetting, Boolean raiseEvnt) +214
   Infragistics.Web.UI.GridControls.SummaryRow.BehaviorEvents_PreRender(Object sender) +665
   Infragistics.Web.UI.GridControls.GridBehaviorEvents.OnPreRender() +22
   Infragistics.Web.UI.GridControls.GridBot.HandlePreRender() +34
   Infragistics.Web.UI.Framework.Data.FlatDataBoundControl.OnPreRender(EventArgs e) +186
   Infragistics.Web.UI.GridControls.WebDataGrid.OnPreRender(EventArgs e) +13
   System.Web.UI.Control.PreRenderRecursiveInternal() +80
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842

Here is part of my code...

Default.aspx:

<asp:RadioButtonList AutoPostBack='true' ID='rblTaskOpenClosed' RepeatDirection='Horizontal' runat='server'>
    <asp:ListItem Selected='true' Text='Open' Value='1' />
    <asp:ListItem Text='Closed' Value='0' />
    <asp:ListItem Text='Both' Value='2' />
</asp:RadioButtonList>
<ig:WebDataGrid AutoGenerateColumns='False' Height='280px' ID='grdTasks' runat='server' Width='96%'>
    <Columns>
        <ig:TemplateDataField Key='Category' Header-Text='Category' Header-Tooltip='Category'>
            <ItemTemplate>
                <asp:Label ID='lblCategory' runat='server' Text='<%#CType(Container, Infragistics.Web.UI.TemplateContainer).DataItem.TaskCategory.Description%>' />
            </ItemTemplate>
        </ig:TemplateDataField>
        <ig:TemplateDataField Header-Text='Reference' Header-Tooltip='Reference' Key='Reference' Width='30%'>
            <ItemTemplate>
                <asp:HyperLink ID='hlTaskReference' NavigateUrl='<%# String.Format("TaskForm.aspx?id={0}&ReturnURL={1}", CType(Container,Infragistics.Web.UI.TemplateContainer).DataItem.ID.ToString, Me.Request.Url.PathAndQuery) %>' runat='server' Text='<%# CType(Container,Infragistics.Web.UI.TemplateContainer).DataItem.Reference %>' />
            </ItemTemplate>
        </ig:TemplateDataField>
        <ig:TemplateDataField Key='Code' Header-Text='Code' Header-Tooltip='Code'>
            <ItemTemplate>
                <asp:Label ID='lblReference' runat='server' Text='<%#CType(Container, Infragistics.Web.UI.TemplateContainer).DataItem.Code%>' />
            </ItemTemplate>
        </ig:TemplateDataField>
        <ig:TemplateDataField Key='Date' Header-Text='Date' Header-Tooltip='Date' Width='15%'>
            <ItemTemplate>
                <asp:Label ID='lblDue_Date' runat='server' Text='<%#IIf(CType(Container, Infragistics.Web.UI.TemplateContainer).DataItem.Task_Date = "#12:00:00 AM#", String.Empty, FormatDateTime(CType(Container, Infragistics.Web.UI.TemplateContainer).DataItem.Task_Date, Microsoft.VisualBasic.DateFormat.ShortDate))%>' />
            </ItemTemplate>
        </ig:TemplateDataField>
        <ig:TemplateDataField Key='UserName' Header-Text='Assigned To' Header-Tooltip='Assigned To' Width='15%'>
            <ItemTemplate>
                <asp:HyperLink ID='hlUserName' NavigateUrl='<%# String.Format("ContactForm.aspx?id={0}&ReturnURL={1}", CType(Container,Infragistics.Web.UI.TemplateContainer).DataItem.UserID.toString, Me.Request.Url.PathAndQuery) %>' runat='server' Text='<%# CType(Container,Infragistics.Web.UI.TemplateContainer).DataItem.User.Name %>' />
            </ItemTemplate>
        </ig:TemplateDataField>
    </Columns>
    <Templates><errortemplate runat='server'>No data</errortemplate></Templates>
    <Behaviors>
        <ig:ColumnResizing />
        <ig:Paging PageSize='15' PagerAppearance='Top' PagerMode='NextPreviousFirstLast' FirstPageText='First' LastPageText='Last' NextPageText='Next' PreviousPageText='Previous' />
    </Behaviors>
</ig:WebDataGrid>

Default.aspx.vb:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    LoadTasks()
End Sub                               

Private Sub LoadTasks()
    If Contact IsNot Nothing Then
        Dim eopen As BooleanWithBoth = CType(rblTaskOpenClosed.SelectedValue, BooleanWithBoth)
        Dim colTasks As ITaskCollection = AppCon.GetAppCon.Factory.TaskCollectionLoadedByContact(Contact.ID, ITaskCollection.TaskCollectionTypes.All, eopen, BooleanWithBoth.True)
        Select Case eopen
            Case BooleanWithBoth.True
                lblTaskCount.Text = String.Format("{0} open tasks", colTasks.Count.ToString)
            Case BooleanWithBoth.False
                lblTaskCount.Text = String.Format("{0} closed tasks", colTasks.Count.ToString)
            Case BooleanWithBoth.Both
                lblTaskCount.Text = String.Format("{0} tasks", colTasks.Count.ToString)
            Case Else
        End Select
        grdTasks.DataSource = colTasks
        grdTasks.DataBind()
    End If
End Sub   

Protected Sub rblTaskOpenClosed_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles rblTaskOpenClosed.SelectedIndexChanged
    LoadTasks()
End Sub