You could add the Facebook Birthday and Event feeds into the calendar section of your Live/Microsoft account on Outlook.com. That's a work around though, and you would lose some functionality like seeing the wall for the event/being able to RSVP through the calendar event on your phone itself. It would work the exact same for birthdays, though. It's an option, though, if you can't get a fix otherwise.
The only other suggestion I might have is to remove and re-add your FB account. It's worth a shot.