registration form error with fb login

Can you let us know the following:
* Are you seeing a Captcha code on the form itself?
* In the Joomla Global Configuration, there's a setting for Captcha. Let us know what that's set to.
* Go to the User Manager and hit parameters. There's another setting for Captcha. Try setting that to "None" and see if the error goes away. If so, let us know what value that setting was at before.

If none of those work, can you let us know if you have any other security-type plugins (firewall, admintools, etc) installed that could be trying to perform checks on form submissions?

Thanks,
Alex