NSAttributedString initialization throws NSRangeException

A shot in the dark: do you ensure that the initialization happens on the main thread?

I had exactly the same problem. I noticed that in my case the exception occurs under reproducible conditions (animations in a UICollectionViewController), but I was unable to find the actual cause. My best guess is that it's a framework bug, so I'd too suggest you file a radar.

I ended up pre-rendering my HTML formatted strings into a cache (aka array) at a time where it works, and then load the NSAttributedStrings from it on demand.

Note though that this solution may not fit your use case, since I only have to deal with a limited amount of formatted strings at a time and hence know the expense of rendering them in advance.

In my case, this was happening because I was trying to instantiate a NSAttributedString from within a UICollectionViewCell that was in detached state (before it was inserted in the parent UICollectionView).