This happened last year. Something on Facebook's end, just have to wait it out. No need to reload the app, just wait it out. If you need to go on FB on your iPhone, go through Safari.
Yeah, it is happening to me, too. So I guess it is a server problem and not the app itself. Well, that's somewhat good news in that they'll probably have it fixed faster this way.
Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_0 like Mac OS X; en-us) AppleWebKit/532.9 (KHTML, like Gecko) Version/4.0.5 Mobile/8A293 Safari/6531.22.7)