Important news for developers using reCAPTCHA on your sites.
If you are currently using http://api.recaptcha.net/challenge?k=XXXX and you need to implement reCAPTCHA on an SSL protected page — you need to switch the links to https://www.google.com/recaptcha/api/challenge?k=XXXYYYZZZ. Per Google, this change went into effect April 2011.
For more information, read this page
