SelectIndexChange Event Of DropDownList not fireing

Hi,I have an app that is using master pages. I've created a new page (called test.aspx) with the code below:<%@ Page Title="" Language="vb" AutoEventWireup="false" MasterPageFile="~/Mancosa.Master" CodeBehind="test1.aspx.vb" Inherits="Mancosa.test1" %> <asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server"> <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"> </asp:DropDownList> </asp:Content>Please note that the master page header is as follows:<%@ Master Language="VB" AutoEventWireup="false" Codebehind="Mancosa.master.vb" Inherits=&q ...