This has become a problem for me - I had to remove all update panels that I had associated with my TabContainer control. Here is a little more info on the problem:
Repro:
In FireFox 2.0.0.2 only...
See below for .aspx file to test against. In short, put a TabContainer inside of an update panel, cause a post back to occur.
Expected:
Postback should occur normally, tab container is updated inline.
Actual:
Javascript exception is thrown, Error.invalidOperation() , in file (I believe) MicrosoftAjax.js, function function Sys$Component$_setReferences(component, references) .
Notes:
* http://www.mozilla.com/en-US/firefox/2.0.0.2/releasenotes/
* Stepping through the code actually seems fine - but I've not done much debugging in this particular portion of Ajax.
<%-- Sample, broken TabContainer inside of Update Panel --%>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajaxToolkit" %>
<html>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="Server" />
<asp:UpdatePanel runat="server" ID="updatePanelForTestControl" UpdateMode="Conditional">
<ContentTemplate>
<ajaxToolkit:TabContainer runat="server" ID="Tabs" ActiveTabIndex="1">
<ajaxToolkit:TabPanel runat="Server" ID="Panel1" HeaderText="Tab 01">
<ContentTemplate>
First tab panel
</ContentTemplate>
</ajaxToolkit:TabPanel>
<ajaxToolkit:TabPanel runat="Server" ID="Panel2" HeaderText="Tab 02" >
<ContentTemplate>
Second tab panel
<asp:Button ID="Button1" runat="Server" Text="Post Back" />
</ContentTemplate>
</ajaxToolkit:TabPanel>
</ajaxToolkit:TabContainer>
</ContentTemplate>
</asp:UpdatePanel>
</form>
</body>
</html>