send javascript variable to asp.net webforms code-behind is always empty

I was using This SO answer as a reference for sending a javascript variable to my server side. However when I implement that solution everything comes up correctly in the js alert(), but the Value of my hidden field when I hit the server is always empty.

Javascript and Html:

<script>
    function rblSelectionChange()
    {
        var selection = $('#inAction input:checked').val();
        var stuff = $('#<%= clientSelection.ClientID %>').val(selection);
        alert(stuff.val());
    }
</script>
<asp:HiddenField ID="clientSelection" runat="server" />
<div class="row-fluid">
    <asp:RadioButtonList runat="server" ID="inAction" ClientIDMode="Static">
        <asp:ListItem onClick="rblSelectionChange();" Value="RuEp" Text="I remember my <b>username</b>. Please email me a new <b>password</b>." />
        <asp:ListItem onClick="rblSelectionChange();" Value="ReEu" Text="I remember my <b>email</b>. Please email me my <b>username</b>." />
        <asp:ListItem onClick="rblSelectionChange();" Value="ReEup" Text="I remember my <b>email</b>. Please email me my <b>username</b> and a new <b>password</b>." />
    </asp:RadioButtonList>
</div>

On the submit event of the page I try to grab the value and it is empty:

protected void btnActionSelect_Click(object sender, EventArgs e)
{
    string selection = clientSelection.Value;
    ...snip...
}

Any idea what I am missing?

UPDATE:

I have tried to change my hidden field to a pure html one, not the asp: control.

<input type="hidden" id="clientSelection" name="clientSelection" value="" />

I have modified the code-behind as follows:

private string _selection = "";
protected void Page_Load(object sender, EventArgs e)
{
    //_selection = clientSelection.Value.ToString();
    if (IsPostBack)
        _selection = Request.Form["clientSelection"];
}

I am still getting nothing for the value Request.Form["clientSelection"]. Important note however is it works in Chrome, FF, and IE10. The browser I am trying to get it to work in is IE 7 8 and 9. If anyone can help me out on this one, it would be greatly appreciated. I am fully stumped.

EDIT: Per request, here is the source of the page when I inspect it in IE10 (with browser and document mode set to IE7)

<DIV id=ctl00_cphBodyWithForm_htmActionSelect class=row-fluid>
    <P class=lead>Can't access your account? Please select from the following options: </P>
    <SCRIPT>
                function rblSelectionChange()
                {
                    var selection = $('#inAction input:checked').val();
                    var stuff = $('#ctl00_cphBodyWithForm_clientSelection').val(selection);
                    alert(stuff.val());
                }
    </SCRIPT>
    <INPUT id=ctl00_cphBodyWithForm_clientSelection type=hidden name=ctl00$cphBodyWithForm$clientSelection jQuery191034119593101524303="7"> 
    <DIV class=row-fluid>
        <TABLE id=inAction border=0>
            <TBODY>
            <TR>
             <TD><INPUT onclick=rblSelectionChange(); id=inAction_0 type=radio value=RuEp name=ctl00$cphBodyWithForm$inAction jQuery191034119593101524303="8"><LABEL for=inAction_0>I remember my <B>username</B>. Please email me a new <B>password</B>.</LABEL></TD>
             </TR>
             ...snip...
            </TBODY>
        </TABLE>
     </DIV>
     <DIV class=span12>
        <A class="submitButton roundedBR" href="javascript:__doPostBack('ctl00$cphBodyWithForm$ctl00','')">Continue &gt; </A>
     </DIV>
</DIV>