为将对象引用到实例[超怪问题]

我在LOGIN的时候给SESSION赋了N个值
代码如下(运行通过/经测试值传进了SEESSION):
protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
    {
        Label1.Text = string.Empty;
        if (string.Compare(Request.Cookies["CheckCode"].Value.ToLower(), txtYZM.Value.ToLower()) != 0)
        {
            Image5.Visible = true;
            Label1.Text = "验证码错误,请输入正确的验证码";
            return;
        }
        else
        {
            SqlConnection LoginCon = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["alockarConnectionString"].ToString());
            LoginCon.Open();
            SqlCommand cmd = new SqlCommand("select * from users where UserName='" + txtUserName.Value.Trim() + "'", LoginCon);
            cmd.CommandType = CommandType.Text;
            SqlDataReader reader = cmd.ExecuteReader();
            if (reader.Read())
            {
                string Manage = reader["Manage"].ToString();
                string Vip = reader["Vip"].ToString();
                string Grade = reader["Grade"].ToString();
                int UserID = reader.GetInt32(0);
                string PassWord = reader["PassWord"].ToString();
                string PassWord0 = txtPassword.Value.Trim();
                if (PassWord == PassWord0)
                {
                    Session["UserID"] = UserID;
                    Session["UserName"] = txtUserName.Value.Trim();
                    Session["Grade"] = Grade;
                    Session["Vip"] = Vip;
                    Session["Manage"] = Manage;
                    Response.Write(ccObj.MessageBoxUrl("登陆成功！", "../Default.aspx"));
                }
                else
                {
                    Response.Write(ccObj.MessageBox("您输入的用户名和密码不正确,请重新输入！"));
                }
            }
            else
            {
                Response.Write(ccObj.MessageBox("您输入的用户名和密码不正确,请重新输入！"));
            }
            /*else
            {
                SqlConnection LoginCon = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["alockarConnectionString"].ToString());
               SqlCommand LoginCmd = new SqlCommand("ValidateLogin", LoginCon);
               LoginCmd.CommandType = CommandType.StoredProcedure;
               LoginCmd.Parameters.Add("@UserName", SqlDbType.VarChar).Value = txtUserName.Value.Trim();
               LoginCmd.Parameters.Add("CryptPassword", SqlDbType.VarChar).Value = txtPassword.Value.Trim();
               LoginCon.Open();
               int userid = Convert.ToInt32(LoginCmd.ExecuteScalar());
               LoginCon.Close();
               if (userid <= 0)
               {
                   Response.Write(ccObj.MessageBox("您输入的用户名和密码不正确,请重新输入！"));
               }
               else
               {

                   Session["UserName"] = txtUserName.Value.Trim();
                   Response.Write(ccObj.MessageBoxUrl("登陆成功！", "../Default.aspx"));
               }
            }*/
        }
    }
然后我在别的页判断SEESION的值时出现错误
代码如下:
if (!IsPostBack)
        {
            if (Session["Manage"].ToString() != "普通用户" || Session["Manage"].ToString() != "超级用户")//?
            {
                LinkButton9.Visible = true;
            }
            else
            {
                LinkButton9.Visible = false;
            }
        }
单步调试 Session["Manage"]有值但的确是以上判断出错
......求高手帮助解决
错误提示:
未将对象引用设置到对象的实例。
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。

异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。

源错误:

行 20:        if (!IsPostBack)
行 21:         {
行 22:             if (Session["Manage"].ToString() != "普通用户" || Session["Manage"].ToString() != "超级用户")//?
行 23:             {
行 24:                 LinkButton9.Visible = true;

--------------------编程问答-------------------- 你写英文的值试下. --------------------编程问答-------------------- if (Session["Manage"] != null && (Session["Manage"].ToString() != "普通用户" || Session["Manage"].ToString() != "超级用户"))

补充：.NET技术 ,  .NET Framework