I think I have found a bug in the iOS 7 Simulat
It appears this is not a Simulator bug, but an iOS 7 bug as I have been able to reproduce it on a device now. I have created a new question for it here: iOS 7 BUG - NSAttributedString does not appear
The bug appears to be the combination of using NSUnderlineStyleAttributeName & NSParagraphStyleAttributeName as attributes for a NSAttributedString.