Hello Hughes,

Since we already integrate recaptcha v2, the old captcha will no longer work with the current system. However there were some issue with displaying new recaptcha on this release. We already fix this internally in our system and the fix will be available in the next release.
I've applied the fix inside your administrator/components/com_easysocial/includes/captcha/adapters/recaptcha.php and components/com_easysocial/themes/wireframe/captcha/recaptcha.js. The recaptcha box should be display properly now.

However it seems like the recaptcha domain for your site is no longer valid as you can see from the screenshot here, http://screen.stackideas.com/2015-03-09_1819.png thus I have re-provide a new recaptcha code for you and the recaptcha is displaying as it should now.
http://screen.stackideas.com/2015-03-09_1836.png

Regarding with your another inquiry, may I know what do you mean by "I've just noticed that registration to my site has changed"? Perhaps you can explain more on the issue. Please advise.