Fatal Error from Facebook Registration Tool

I am wanting to use facebook to register on my website, but since I got the Facebook Registration Tool plugin I am now getting this Fatal Error message when I try to go to my website. Also wordpress.com does not recognize my username anymore, so I cannot login to my dashboard. Here is the exact msg I am getting…

Fatal error: Cannot redeclare class FacebookApiException in /hermes/bosweb/web119/b1192/ipg.bcfitnessus/wp-content/plugins/facebook-registration-tool/libs/facebook.php on line 91

Please help!!!