Do you have a toolbar or some addition to the browser? I have often had issues with toolbars messing forms!
//Oh! THANKS!!!
It worked for me the first time: FF3 Vista/ (with Firebug enabled).
Are you testing on preview from the Manager? I’ve seen some weirdness in $_SESSION variables (which captcha uses to store the correct response) when visiting from the Manager.
Another thing to try is clearing your browser cache (including cookies) before visiting the page. You may have something in there from an earlier visit or Manager session that’s hosing things.
