BuddyPress.org

@Greg, I get that message:

This application is not set up to request your email address

That is weird. But then the page forwards to a white page with just this text:

Error: Failed to get the Facebook session. Please verify your API Key and Secret.

That still looks like the most likely cause. Make sure you copied the right numbers and that they were saved in the plugin. The save buttons in the admin area are a bit tricky. I think they are separate forms, so you have to hit the right button.