Hi Sun,
Thanks for the quick response.
The page does call comment_form().
I took a look at the Twenty Twelve theme as you suggest, and the call is isolated and looks identical.
You mention filters and actions. Is there something else I may not be initializing that would prevent the Mollom plug-in from displaying the captcha?
I was wondering if the fact that the plug-in can display the error message was of help to you. Would it help to provide an admin login to the site?
Appreciate the help.
Regards,
Elliot