getting the htmlEditorExtender to work

I have a Visual Basic project that has some ajax controls in the toolbox, but it didn't have the htmleditorcontrol, which I wanted to use.  

I did have the ajaxcontroltoolkit dll in my bin folder.  So I right clicked on the toobox, and I selected 'choose items", then I browsed to my bin folder and selected that dll.  As I hoped, a whole of set of new controls, including the one I wanted, got added.

So I went to my webform, where I have a textbox that I wanted to convert to an html editor.  There was an arrow on my textbox, I clicked on that, and I selected "add extender".  I chose the htmleditorextender, and at first sight, it seemed to work. 

It produced the following html:

<asp:TextBox ID="TextBoxContents" runat="server" Height="500px" style="margin-left: 0px" 
           TextMode="MultiLine" Width="900px" ClientIDMode="Static"></asp:TextBox><asp:HtmlEditorExtender ID="TextBoxContents_HtmlEditorExtender" runat="server" Enabled="True" TargetControlID="TextBoxContents"></asp:HtmlEditorExtender>

I also set

EnableSanitization="false"

and put a scriptmanager in the form above it.

I find that the HtmlEditorExtension simply has no effect at all on the production server - the textbox still looks like a textbox, and in my local pc, it gives errors about the UI.

Any help is appreciated.

Thanks.