Facebook RSVP not working / Twitter works

we have installed events+ and really need users to have the ability to rsvp via their facebook login, but it doesn't seem to be working properly.

sample event is located here: http://blog.kwwaterford.com/events/2012/04/sample-traning-event/

clicking the twitter login works fine (launches the popup), but facebook seems to do nothing.

need this relatively quickly, but any help at all would be greatly appreciated.

thanks.