Recently our team spent several days debugging a problem connecting to the Facebook API from our production servers running CentOS. Everything worked perfectly in development for our iFrame application and our Facebook connect code. After exhaustive debugging, it turned out to be an issue with the headers Curl was using. To fix, edit facebooker/lib/facebooker/service/curl_service.rb and add line 6 below.
Hope this helps someone avoid this issue in the future.