It sounds like you've set an IP Whitelist in your Facebook Application configuration. You'll need to edit your application information and remove that restriction.
If it's not that, it could be that you're on a shared host and Facebook has blocked that IP address due to abuses by other websites on that server. There's not much we could do about that other than recommend contacting your provider and moving you to a different IP address.
I hope that helps,
Alex
Facebook API Error: This IP can't make requests for that application
