recaptcha registration issue

Hello

I am having an issue getting the google reCAPTCHA working.
If i don't have it showing im getting heaps of fake users joining up and when i do have it showing I get an error message

"There was some error in the registration form. Please proceed with full registration."

And you still cant register when you fill out the details again.

Wish you would do your own spam filter in the registration.

Anyway could you please help with this not sure what i am setting up wrong.

Thanks Adam