I believe there was a temporary problem with facebook app as many people, myself included had the same issue. Mines working fine now. I didn't do or change anything it just snapped back into action.
Im still having the same problem both with the app and through facebook.com. I would guess they are having problems at their end. Look like I will have to find something else to do to waste time...
Facebook itself is the problem, not the iPhone app. Even on the web version every time you do a refresh of the news feed something else come up . Give them some time.