Originally Posted by
Mystic
That actually happened to me when they first updated to work with ios7. I had to reallow facebook because it was shut off for some reason, and when I toook a screenshot it would be facebook's white screen frozen, then would start to flip back and forth from era to facebook. If that's happening to you, just leave it that way for awhile and if it doesn't start doing something like from above you might have to keep trying out other ways to fix it.
(You might have a different problem that might need to be fixed if it's not allowing it)
What device do you have?