I found out what caused the problem with my n9. I tried to share a picture through Epic Fail app (from Ovi store). The sharing wen't ok, but the picture didn't actually get shared in my timeline.

After this the facebook online status has been stuck in "account in use" everytime I try to go online. The app works otherwise normally.

Haven't found yet the solution how to get the facebook-sync work again. Something to do with Nokia servers and sharing maybe.