RE: TabContainer not loading sporadically

I have page with two different TabContainers.
Sometimes when the page is loaded I get the error.

Sys.InvalidOperationException: Component 'TabContainer1' was not found.

Then both TabContainers are not loaded and are completely blank. I personally only have seen this a couple of times, but my client says it happens everyday sporadically. They close the page down and reopen it and it loads fine.

The page does not have a MasterPage. Some of the TabPanels do have UpdatePanels in them, but there is no UpdatePanel around the whole TabContainer.

I have tried changing the ScriptManager to below but did not work.

   <ajaxToolkit:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server"> 
    </ajaxToolkit:ToolkitScriptManager> 

Thanks