Ajax Website working fine in Chrome and Firefox but not with IE 8 and 9

Hello,

The following code is working fine with Firefox and Chrome, which is, when I click on the first radio button it postback and keep the value but in IE it is not keeping the value. Why is it working like this?

Below is the code:

<%@ Page Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeBehind="Default.aspx.cs"
    Inherits="ParallelOpsChooseEvolverPage._Default" %><%@ Register Assembly="ParallelOpsChooseEvolverPage" Namespace="ParallelOpsChooseEvolverPage.Controls"
    TagPrefix="ParallelOpsChooseEvolverPage" %><%@ Register Src="~/Controls/AdTypeSelector.ascx" TagName="AdTypeSelector" TagPrefix="poce" %><asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent"><title>Page de redirection vers le guichet virtuel correspondant selon le titre et rubrique
        choisi</title><script src="Scripts/jquery-1.4.1.js" type="text/javascript"></script><script type="text/javascript" src="Scripts/MiscScripts.js"></script></asp:Content><asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent"><asp:ScriptManager runat="server" ID="ScriptManager1" EnablePartialRendering="true"></asp:ScriptManager><asp:UpdatePanel runat="server" ID="updatePanel1" UpdateMode="Always" ChildrenAsTriggers="True"><ContentTemplate><div id="mainContent"><div id="normalClientContainer"><h2>
                        Rubrique et types d'annonces</h2><div id="clientTypeTitleContainer" class="titleContainer"><span class="titles">Annoncez-vous pour une raison privée ou commerciale?</span></div><div id="clientContainer"><asp:RadioButtonList ID="rblClientType" runat="server" AutoPostBack="true" RepeatDirection="Horizontal"
                            CssClass="radioButtonListContainer" RepeatLayout="Table" OnSelectedIndexChanged="ClientTypeChanged"><asp:ListItem Text="Annonce Privée" Value="p" /><asp:ListItem Text="Annonce commerciale" Value="g" /></asp:RadioButtonList></div><div id="dropDownListContainer"><div id="marketChoosetitleContainer" class="titleContainer"><span class="titles">Choisissez votre marché et votre rubrique</span></div></div><div id="publicationContainer"><div class="labelContainer"><asp:Label ID="lblPublication" runat="server" Text="Publication:" CssClass="label" /></div><asp:DropDownList CssClass="ddlist" ID="ddlPublication" runat="server" AutoPostBack="true"
                            OnSelectedIndexChanged="PublicationChanged" /></div><div id="marketContainer"><div class="labelContainer"><asp:Label ID="lblMarket" runat="server" Text="Marché:" CssClass="label" /></div><asp:DropDownList CssClass="ddlist" ID="ddlMarket" runat="server" AutoPostBack="true"
                            OnSelectedIndexChanged="MarketChanged" /></div><div id="categoryContainer"><div class="labelContainer"><asp:Label ID="lblCategory" runat="server" Text="Catégorie:" CssClass="label" /></div><asp:DropDownList CssClass="ddlist" ID="ddlCategory" runat="server" AutoPostBack="true"
                            OnSelectedIndexChanged="CategoryChanged" /></div><div id="rubricContainer"><div class="labelContainer"><asp:Label ID="lblRubric" runat="server" Text="Rubrique:" CssClass="label" /></div><asp:DropDownList CssClass="ddlist" ID="ddlRubric" runat="server" OnSelectedIndexChanged="RubricSelected"
                            AutoPostBack="true" /></div><div id="adTypesContainer" runat="server"><div id="adTypesTitleContainer" class="titleContainer"><span class="titles">Quel type d'annonce désirez-vous publier?</span></div><poce:AdTypeSelector runat="server" AdTypeControlSize="Small" ID="atsPA" RadioButtonText="Petite annonce"
                            ImageUrl="~/Assets/PA.png" ContainerDisplayStyle="none" /><poce:AdTypeSelector runat="server" AdTypeControlSize="Small" ID="atsPAPhoto" RadioButtonText="Petite annonce photo"
                            ImageUrl="~/Assets/PAPhoto.png" ContainerDisplayStyle="none" /><poce:AdTypeSelector runat="server" AdTypeControlSize="Small" ID="atsupload" RadioButtonText="Annonce finie - upload"
                            ImageUrl="~/Assets/Upload.png" ContainerDisplayStyle="none" /><poce:AdTypeSelector runat="server" AdTypeControlSize="Small" ID="atsModule" RadioButtonText="Module"
                            ImageUrl="~/Assets/Module.png" ContainerDisplayStyle="none" /><poce:AdTypeSelector runat="server" AdTypeControlSize="Big" ID="atsMM" RadioButtonText="Annonce à composer mm"
                            ImageUrl="~/Assets/MM.png" ContainerDisplayStyle="none" /><asp:HiddenField runat="server" ID="hdCheckAdType" Value="" /></div><div id="errorContainer"><asp:Label ID="lblErrorMessage" runat="server" Text="" /></div><div class="em_bg4" style="width: 100%; display: none" runat="server" id="ConfirmButtonConfirmation"><div id="em_aufgabe_next" style="padding: 9px 20px 9px 9px;"><asp:LinkButton ID="LinkButton1" class="buttonorange" OnClick="ConfirmChoice" runat="server"
                                PostBackUrl="Default.aspx"><img src="Assets/next-step.png" border="0" alt="" /></asp:LinkButton></div><div class="clr"><br></div></div><div id="DebugContainer"><asp:Label runat="server" ID="lblDebug" /></div></div></div></ContentTemplate></asp:UpdatePanel></asp:Content>

Thank you for your help!