Deserialization failure,Invalid response

Error i'm getting after pressing on sort

DotNetNuke.Services.Exceptions.PageLoadException: Kan geen voorlooptekens (..) gebruiken voor afsluiten boven de hoogste map. ---> System.Web.HttpException: Kan geen voorlooptekens (..) gebruiken voor afsluiten boven de hoogste map. bij System.Web.Util.UrlPath.ReduceVirtualPath(String path) bij System.Web.Util.UrlPath.Reduce(String path) bij System.Web.UI.Control.ResolveClientUrl(String relativeUrl) bij Infragistics.Web.UI.GridControls.Sorting.AddHeaderImgToCaption(GridField column, SortDirection direction) bij Infragistics.Web.UI.GridControls.Sorting.BehaviorEvents_PreRender(Object sender) bij Infragistics.Web.UI.GridControls.GridRenderer.RenderContents(HtmlTextWriter writer) bij Infragistics.Web.UI.Framework.RunBot.HandleRenderContents(HtmlTextWriter writer, RendererBase renderer) bij Infragistics.Web.UI.Framework.Data.FlatDataBoundControl.Render(HtmlTextWriter writer) bij ASP.desktopmodules_autorisatie_autorisatie_view_ascx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij DotNetNuke.UI.Modules.ModuleHost.RenderContents(HtmlTextWriter writer) bij System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) bij System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) bij ASP.default_aspx.__Render__control1(HtmlTextWriter __w, Control parameterContainer) bij System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) bij System.Web.UI.Page.Render(HtmlTextWriter writer) bij System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- Einde van intern uitzonderingsstackpad ---

My vb code for sorting:

Protected Sub WebDataGrid1_ColumnSorted(ByVal sender As Object, ByVal e As Infragistics.Web.UI.GridControls.SortingEventArgs) Handles WebDataGrid1.ColumnSorted

        If e.Column.Key = "Username" Then

            Dim dir As Infragistics.Web.UI.SortDirection = e.SortedColumns(e.Column.Key).SortDirection
            e.SortedColumns.Add("Username", dir)
            e.SortedColumns.Add(e.Column.Key, dir)

        End If

    End Sub

My Asp Code:

<ig:WebDataGrid ID="WebDataGrid1"
                 runat="server"
                 AutoGenerateColumns="False"
                 Height="350px"
                 Width="697px"
                 style="margin-bottom: 4px" EnableAjax="False">
    <Columns>

<%--   COLUMN USER_ID--%>
        <ig:BoundDataField DataFieldName="UserID"
                           Key="UserID"
                           Hidden="True"
                           Width="50px">
            <Header Text="UserID" />
        </ig:BoundDataField>

</Columns>
     <Behaviors>
          <ig:ColumnResizing>
         </ig:ColumnResizing>
          <ig:Sorting SortingMode="single" Enabled="true" EnableInheritance="True">
                <ColumnSettings>
                    <ig:SortingColumnSetting ColumnKey="Username" />

                </ColumnSettings>
            </ig:Sorting>
     </Behaviors>
   </ig:WebDataGrid>