Asp.Button will not fire

I have a button that will not fire no matter what I do. Other butons on that page work fine and a simmilar buton on a different page also works fine.  I first set the Click property to a codebehind function - it did not work. I then removed the property and set the OnClientClick to a javascript function where I issue a __doPostBak - it did not work either (I have a break point in the OnLoad() event). This button happens to be in a table used for ModalPopup, but I am not sure if this has any impact as a similar button in another page does work fine. My code is pasted below, button is 'btnOK'. Ideas anyone?
<%@ Page Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="false" CodeFile="OrderBTESubmit_new.aspx.vb" Inherits="OrderBTESubmit_new" title="Order Submission" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPr ...