So I'm using recaptcha 1.2 with Captcha 2.0-rc2 and this causes each page with recaptcha to go blank (says "read api.recaptcha.net").
So I install Captcha 1.0-rc2 and this causes each comment post with recaptcha to be "Invalid captcha token". It refuses to post.
Bear in mind, I am also using AJAX Comments module (so perhaps this has been a cause). This seems to be pretty urgent bug, I recommend quickly trying a recaptcha 1.2, captcha 2.0-rc2, and ajax comments the latest, combination and quickly patching this.