Export to Excel Exception

I am running the canned Admin forms for a simple database.  I found where to turn Excel export on in the GridViews.  I have included the registerPostBack code listed elswhere and am executing this on the GridView's preRender Event.  However, I am still blowing up in EntityGridView.Export on line 919, htmlForm.RenderControl(htmlWriter) with RegisterForEventValidation can only be called during Render().

 I appreciate any help.

This works for me... or is this what you used? 

    /// <summary>
    /// Fixes AJAX error when you click "Export to Excel" after you've made a previous AJAX callback
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void egv1_OnPreRender(object sender, EventArgs e)
    {
         registerPostBack();
    }

    private void registerPostBack()
    {
        System.Collections.Generic.IList<Control> list = FormUtil.FindControls(EntityGridView1, "lnkExport");

        if (list.Count > 0)
        {
            LinkButton lnkExport = list[0] as LinkButton;
            ScriptManager sm = ScriptManager.GetCurrent(this.Page);
            if (sm != null)
                sm.RegisterPostBackControl(lnkExport);
        }
    }