this._form is null error with ScriptManager and Ajax Control Toolkit

Question

I'm using the Ajax Control Toolkit with .NET in VS2008 to put a Rating control on my page. I've got the scriptmanager on the page and the rating control works in Chrome and IE but not Firefox. In Firefox it gives me this error "this._form is null". I've got no other scripts included on the page. There are a couple included in the master page but they are closed with </script>. I've tried using ToolkitScriptManager but it hasn't changed anything.

   <form id="aspnetForm" runat="server"><ajaxToolkit:ToolkitScriptManager id="ScriptManager1" runat="server" EnableScriptGlobalization="true" EnableScriptLocalization="true" EnablePartialRendering="true" SupportsPartialRendering="true" />
<div id="main" align='center'>

<div id="inside">
<div id="nav">
    <div id="photoCount"><label id="lblPhotoCount" runat="server"></label></div>
    <div id="photoNav">
        <a class="nav_a" runat="server" id="previouslink" href="">Previous</a><a class="nav_a" runat="server" id="nextlink" href="">Next</a> 
    </div>
    <div class="clear"></div>
</div>
<div id="divBrowseBox" runat="server">
    <div id='divPicHeader' runat='server' style="z-index: 2998">
    </div>
</div>

<div id="likeArea">
  <iframe id="likeIframe" runat="server" src="" scrolling="no" frameborder="0" style="border:none; overflow:hidden; width:250px; height:80px;" allowTransparency="true"></iframe>
</div>

<div id="ratingArea">
    <asp:updatepanel id="UpdatePanel1" runat="server">
        <ContentTemplate>
        <asp:HiddenField ID="hdnCurrentPhotoID" runat="server" />
        <asp:HiddenField ID="hdnCurrentRating" runat="server" />
        <asp:HiddenField ID="hdnAvgRating" runat="server" />
        <asp:HiddenField ID="hdnTotalVotes" runat="server" />
        <asp:HiddenField ID="hdnAddRating" runat="server" />

        <asp:Label ID="lblYourVote" runat="server" Font-Size="12px" Text="Rate This Photo!"></asp:Label>
        <div id="starbox">
        <div id="stars">
        <ajaxToolkit:Rating ID="Rating1" runat="server"
            CurrentRating="3"
            MaxRating="5"
            StarCssClass="ratingStar"
            WaitingStarCssClass="savedRatingStar"
            FilledStarCssClass="filledRatingStar"
            EmptyStarCssClass="emptyRatingStar"
            OnChanged="Rating1_Changed"
            AutoPostBack="true"
            BehaviorID="rbid"
        >
        </ajaxToolkit:Rating>
        </div>
        </div>
        <div style="clear: both;"></div>
        <asp:Label ID="lblTotalVotes" runat="server" Font-Size="10px" Text=""></asp:Label>

        </ContentTemplate>
    </asp:updatepanel>
</div>
<div style="clear: both;"></div>

</div>

</div>
</form>

Updated with code. There are only some styles above the form and that is all.