Adding ScriptManager makes Request never complete - asp.net

Question

I have a very strange problem. Initially, my page is working fine, if I click a "Back" button, it will navigate to the previous page. But when I add this line
<asp:ScriptManager ID="ScriptManager" runat="server"></asp:ScriptManager>
Everything seems to stop working. Clicking the button causes the request to never complete (i.e. I cannot go back to previous page when I click "Back" button).
My page structure looks like this
<%# Page Title="" Language="C#" MasterPageFile="~/Master/Main.Master" AutoEventWireup="true" CodeBehind="dsp_FileName.aspx.cs" Inherits="[Namespace].dsp_FileName" %>
<%# MasterType VirtualPath="~/Master/Main.Master" %>
<asp:Content ID="C1" ContentPlaceHolderID="PageContent" runat="server">
<script type="text/javascript">
...
</script>
<asp:ScriptManager ID="ScriptManager" runat="server"></asp:ScriptManager>
<div>
...
</div>
</asp:Content>
Am I missing something?

Answer 1

This problem occurs because in my master page, I have the following snippet:
<form id="frmMain" runat="server" onsubmit="progressStart('Please wait...');">
Basically I wanted to block any other input when user clicks a button. So I need to modify the above snippet to be :
<form id="frmMain" runat="server" onsubmit="progressStart('Please wait...'); return true;">
And in the page where I need to use the Script Manager, I need to add the following code.
function pageLoad() {
if (args.get_isPartialLoad()) {
jQuery.ajax({
type: "GET",
url: "../../JS/Javascript.js",
dataType: "script",
cache: true
});
$('#dErr').dialog('destroy'); // this is the dialog that will show inside the progressStart function.
}
}