I too have just started receiving the same error. I have reauthorised the account, and also removed the app from my facebook settings to start a fresh auithentication, but this still fails. I have even reinstalled Lightroom, to no avail. HELP!
P.S. I too am a Mac LR 4.1 user
Problems solved! This was sourced from a comment on the interweb
"Debug:1169: Error reply from Facebook: (#240) Requires a valid user is specified (either via the session or via the API parameter for specifying the user.
I found out the fix.
Access your facebook fanpage when you are logged into your personal account. There is a new “voice” section and make sure “You are posting, commenting, and liking as the fanpage” not as your main profile. This will stop the error #240.
Hope that helps"
Message was edited by: gervank
Odd as it may seem, that did the trick. But I did have to the "voice" selection switch back and forth for the second album (although that might have something to do with both collections having already defined in LR).
Thanks for the help!