Our sources say that Facebook did a little upgrade to their platform and it is breaking applications willy-nilly.
From what I am hearing is that the platform was upgraded to reflect the privacy changes announced recently. It seems the default security settings are more stringent and as a result app developers are having tough time making API calls. These problems are being talked about on their developer forums as well.
Meanwhile I am tracking this down with Facebook and get a better picture of what is going on. Stay tuned! Are you one of the app writers who is having problems? If yes, write to us and let us know what kind of problems are you experiencing.