Well, this is puzzling. I'm not sure I can make a diagnosis on the info I have. Would you be able to share the social portion of your configuration? Not just the ConnectController, but the entire social configuration.
I also wonder if there may be some conflicting versions in play. ConnectController picks which interceptors to call based on the API binding interface that ConnectInterceptor is parameterized with. Sure, you've got it parameterized with Facebook, but is it the same Facebook? I've seen this kinda thing happen (not with Spring Social, but in other contexts) where there'd be 2 or more of a dependency in the classpath and one would be used for some things and another used for other things. If that's the case here, it may be looking for Facebook from dependency 1, but the interceptor is for Facebook from dependency 2.
That may not be the problem, but if it is, it's an easy thing to check for: Just look to see if you have more than one spring-social-facebook dependency in your WEB-INF/lib. If so, then that's gotta be it.
Spring Social Project Lead