Mysterious Exception

<%@ Application Language="C#" %>
 
<script RunAt="server">
    
    void Application_Start(object sender, EventArgs e)
    {
 
    }
 
    void Application_End(object sender, EventArgs e)
    {
 
    }
 
    void Application_Error(object sender, EventArgs e)
    {
        Exception ex = Context.Error;
        if (ex is HttpUnhandledException)
        {
            ex = Context.Error.InnerException;
        }
 
        ClassLib.Logging_Libraries.ErrorReporter ErrReport = new ClassLib.Logging_Libraries.ErrorReporter("Thenga_Global.cs", 23);
        ErrReport.LogExc(ex);
    }
 
    void Session_Start(object sender, EventArgs e)
    {
        ClassLib.Website_Libraries.BrwrSessManager SessManager = new ClassLib.Website_Libraries.BrwrSessManager();
        SessManager.LoadSessions();
 
        if (System.Web.HttpContext.Current.User.Identity.IsAuthenticated)
        {
            int CustomerID = -1;
 
            ClassLib.Utility_Libraries.AuthManager Auth = new ClassLib.Utility_Libraries.AuthManager();
            CustomerID = Auth.GetUserID(System.Web.HttpContext.Current.User.Identity.Name);
 
            if (CustomerID != -1)
            {
                SessManager.CustomerID = CustomerID;
            }
            else
            {
                FormsAuthentication.SignOut();
                SessManager.CustomerID = -1;
            }
        }
        else
        {
            FormsAuthentication.SignOut();
            SessManager.CustomerID = -1;
        }
        
        //CHECK IF SEARCH BOT/SPIDER
        //--------------------------
        bool IsUncomonUser = false;
        string UncomonName = "";
 
        if (HttpContext.Current.Request.Browser.IsMobileDevice)
        {
            IsUncomonUser = true;
            UncomonName = "mobile";
        }
        else if (HttpContext.Current.Request.Browser.Crawler)
        {
            IsUncomonUser = true;
            UncomonName = "botspider";
        }
        else
        {
            string userAgent = HttpContext.Current.Request.UserAgent.ToLower();
            string[] botKeywords = new string[10] { "bot", "spider", "google", "yahoo", "search", "crawl", "slurp", "msn", "teoma", "ask.com" };
            foreach (string bot in botKeywords)
            {
                if (userAgent.Contains(bot))
                {
                    IsUncomonUser = true;
                    UncomonName = bot;
                }
            }
        }
 
        if (IsUncomonUser)
        {
            //FIGURE OUT HOUR PERIOD
            //----------------------
            int HourPeriodIndex = 1;
            if (DateTime.Now.Hour % 2 != 0)
            {
                HourPeriodIndex = DateTime.Now.Hour + 1;
            }
            else
            {
                HourPeriodIndex = DateTime.Now.Hour;
            }
 
            //CREATE UNCOMONUSER SESSION ID
            //-----------------------------
            string SessionIP = System.Web.HttpContext.Current.Request.UserHostAddress.Replace(".", "");
            string SessionDate = DateTime.Now.Day.ToString() + DateTime.Now.Month.ToString() + DateTime.Now.Year.ToString() + HourPeriodIndex.ToString();
            string SessionBrowser = HttpContext.Current.Request.Browser.Browser + HttpContext.Current.Request.Browser.MajorVersion;
            
            SessManager.SessionID = UncomonName + SessionIP + SessionDate + SessionBrowser;
        }
        else
        {
            SessManager.SessionID = HttpContext.Current.Session.SessionID;
        }
 
        //CREATE OR REUSE SESSION
        //-----------------------
        ClassLib.Website_Libraries.DBSessionManager DBSessManager = new ClassLib.Website_Libraries.DBSessionManager();
        if (DBSessManager.CheckSessionExists())
        {
            if (!DBSessManager.CheckSessionUsable())
            {
                Session.Abandon();
                Response.Cookies.Add(new HttpCookie("ASP.NET_SessionId", ""));
                Response.Redirect("~/Default.aspx");
                return;
            }
        }
        else
        {
            DBSessManager.CreateDBSession();
        }
 
        ClassLib.Website_Libraries.WebsiteQueryBuilder CharityFocusSess = new ClassLib.Website_Libraries.WebsiteQueryBuilder();
        SessManager.CharityFocusID = CharityFocusSess.GetCharityFocus();
    }
 
    void Session_End(object sender, EventArgs e)
    {
        Session.Abandon();
    }
       
</script>

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