Uninstall Facebook. Reinstall Facebook but log in with a different set of login credentials (create a new FB account if necessary). Log out, and log back in with your standard credentials (the one you normally use) and it should fix the issue. This worked back when I had the same issue on their v5.2.X release a little while back. It solved the problem, and I've yet to have that same problem come up again on my phone. On my iPad, same thing happened 2 weeks ago, did the same thing, and no recurring problems yet