Same problem here (in Greek).
I flushed the permalinks several times, also saved the forum settings and ran several repair routines with no result, even when I log out and back in.
The problem had “fixed itself” for a number of days, without me doing anything particular (I had given up on it at the time) and re-appeared yesterday. I remember trashing and deleting a topic before it happened, but I can’t be sure if that was relevant.
