Try to examine active instances and check if captcha is fully loaded or not there.
Does it happen with other templates?

Ignoring AJAX has no icon in this toolbar. Do you have this action in template?
I don't know what is going on with your setup Indy. I ran 1000 through last night and all of them look like this... http://screencast.com/t/4o1ZsP0v
And I have all 3 checkboxes ticked.