Fonte: sgoodger.wordpress.com/2011/02/11/twitter-to-facebook/, questa "potrebbe essere" una soluzione, io ho lo stesso problema ma non ho ancora provato seguire quelle istruzioni semplicemente perché non mi va di inviare test tweets
There is a quick and easy fix to that problem and it goes like this:
Login to Facebook Go to apps.facebook.com/twitter/ If it looks like you?re already connected to Twitter, click the link that says ?want to disconnect??? When disconnected, sign out of twitter from the Facebook app Head back to twitter and send a test tweet (which won?t appear on Facebook) Go back to apps.facebook.com/twitter/ Sign back into Twitter from the Facebook app Ensure the relevant check boxes are ticked Go back to Twitter and send another test tweet, and? Check your Facebook wall ? it should have worked!