Issue with security keys for DNS name and IP address (Input error: Invalid referer)

My website is accessed through DNS name or the IP address.I'm in doubt regarding the security keys generation.Currently, I've generated only the key for the DNS name and it works perfectly.But, when my website is accessed using the IP address, the captcha becomes invisible and generates this message: "Input error: Invalid referer".Did someone have the same issue (and how to solve it)? -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://groups.google.com/group/recaptcha. For more options, visit https://groups.google.com/groups/opt_out.