It looks like there is currently an intermittent (i.e. on/off, hard to replicate consistently) problem with Facebook authentication. Some users may see this error when we try and post to their Facebook Page:
error 240: Facebook rejected the post because of an invalid user
As far as we can tell this is caused by a current problem at Facebook’s end, there have been a number of bugs reported around it, including this one: http://developers.facebook.com/bugs/380937985301371
This appears to affect a number of applications, not just Twitterfeed, so we’re hoping that there will be a resolution soon.
In the meantime, although we can’t say if this will always work, all we can suggest is to re-authenticate your feed at Facebook, for details of how that’s done see this link: http://help.twitterfeed.com/knowledgebase/articles/88139-how-do-i-reconnect-a-facebook-account-h
As we said, because the bug appears to be intermittent, we can’t guarantee that the above re-connecting of your feeds will solve the issue for everyone.
Apologies for the inconvenience, we’ll update this post once we have more details information and/or and update from Facebook.
UPDATE: this issue has been reported fixed by Facebook