Simple and cool login widget for your WordPress! AJAX, support SSL, show avatar, profile button, register and lost password forms...
Check that you've correctly entered both private and public keys in the "Sexy Login" plugin options.
That's one of the problems of cache systems. We can't modify third party plugins.
If you are using another plugin that also uses "reCAPTCHA" it is possible that one of the two "reCAPTCHA" doesn't work correctly. The reason is that "reCAPTCHA" only allows one instance on each page.