Column '2013-02-19' does not belong to table .

I'm not performing a postback and I don't have anything being called during Page Load or Init. The fields that are aggregated are whole integers.The columns displayed would be something like, 2013-02-19, 2013-02-20, 2013-20-21... again, this works fine if I don't use the grid group by expression and I can group manually... I'm trying to have the grouping by default.

Below is my ASPX:

<telerik:RadGrid ID="RG_SLASummary" runat="server" CellSpacing="0" DataSourceID="SDS_SLASummary" GridLines="None" ShowGroupPanel="True" style="margin:10px" ShowFooter="True" Height="750" OnColumnCreated="RG_SLASummary_ColumnCreated">

    <ClientSettings AllowColumnsReorder="True" AllowDragToGroup="True" ReorderColumnsOnClient="True">

        <Selecting AllowRowSelect="True" />

        <Scrolling AllowScroll="True" UseStaticHeaders="True" />

    </ClientSettings>

    <AlternatingItemStyle Width="100px" />

    <GroupHeaderItemStyle Width="100px" />

    <GroupingSettings RetainGroupFootersVisibility="true" />

    <MasterTableView DataSourceID="SDS_SLASummary" ShowGroupFooter="true">

        <GroupByExpressions>

            <telerik:GridGroupByExpression>

                <SelectFields>

                    <telerik:GridGroupByField FieldName="Region" FieldAlias="Region" />

                    <telerik:GridGroupByField FieldName="Status" FieldAlias="Status" />

                    <telerik:GridGroupByField FieldName="Scheduler" FieldAlias="Scheduler" />

                </SelectFields>

                <GroupByFields>

                    <telerik:GridGroupByField FieldName="Region" />

                    <telerik:GridGroupByField FieldName="Status" />

                    <telerik:GridGroupByField FieldName="Scheduler"  />

                </GroupByFields>

            </telerik:GridGroupByExpression>

        </GroupByExpressions>

        <SortExpressions>

            <telerik:GridSortExpression FieldName="Region" SortOrder="Ascending" />

            <telerik:GridSortExpression FieldName="Status" SortOrder="Ascending" />

            <telerik:GridSortExpression FieldName="Scheduler" SortOrder="Ascending" />

        </SortExpressions>

        <CommandItemSettings ExportToPdfText="Export to PDF"></CommandItemSettings>

        <RowIndicatorColumn Visible="True" FilterControlAltText="Filter RowIndicator column">

            <HeaderStyle Width="20px"/>

        </RowIndicatorColumn>

        <ExpandCollapseColumn Visible="True" FilterControlAltText="Filter ExpandColumn column">

            <HeaderStyle Width="20px"/>

            <ItemStyle Width="20px" />

        </ExpandCollapseColumn>

        <EditFormSettings>

            <EditColumn FilterControlAltText="Filter EditCommandColumn column"></EditColumn>

        </EditFormSettings>

    </MasterTableView>

    <EditItemStyle Width="100px" />

    <FilterItemStyle Width="100px" />

    <ActiveItemStyle Width="100px" />

    <ItemStyle Width="100px" />

    <SelectedItemStyle Width="100px" />

    <FilterMenu EnableImageSprites="False"></FilterMenu>

</telerik:RadGrid>

 

<asp:SqlDataSource ID="SDS_SLASummary" runat="server" ConnectionString="<%$ ConnectionStrings:CWFMO %>" SelectCommand="ESP_SchedulerSLASummary" SelectCommandType="StoredProcedure">

    <SelectParameters>

        <asp:ControlParameter ControlID="RDP_StartDate" DbType="Date" Name="startdate" PropertyName="SelectedDate" />

        <asp:ControlParameter ControlID="RDP_EndDate" DbType="Date" Name="enddate" PropertyName="SelectedDate" />

    </SelectParameters>

</asp:SqlDataSource>

Below is my code behind:

protected void RG_SLASummary_ColumnCreated(object sender, GridColumnCreatedEventArgs e)

        {

            if (e.Column is GridNumericColumn)

            {

                GridNumericColumn gridNumericColumn = (GridNumericColumn)e.Column;

                gridNumericColumn.Aggregate = GridAggregateFunction.Sum;

            }

        }