Although I have not checked this thoroughly, it seems that logging out of KDE, switching to a text terminal, logging in there and issuing sudo poweroff induces a clean shutdown. Shutting down from within KDE (often?) gives behaviour as described by this bug.
Also: I am affected by this problem even though I don't have the symlink messup Bert Voegele describes in comment #12.
Although I have not checked this thoroughly, it seems that logging out of KDE, switching to a text terminal, logging in there and issuing sudo poweroff induces a clean shutdown. Shutting down from within KDE (often?) gives behaviour as described by this bug.
Also: I am affected by this problem even though I don't have the symlink messup Bert Voegele describes in comment #12.