This is our site http://www.jglobe.org/
when you go over there a popup will appear and you can see a button LoginwithFacebook.
when you click on this button facebook login page will appear and you will provide the facebook username and password after that popup will disappear but you will not register and login in the site through buddypresss.
Sometime page will refresh but popup appear again for login.
If you need any other info please ask me. I am waiting your reply.