Black screen flicker 1 frame, across several projects, ios

Its not a huge issue but recently the screen flicks black for one frame its usually when the app has been running for 20 seconds or so, on iOS devices.

I've only noticed this in recent builds and considering it happens on 4 separate projects with very different content, I reckon its a bug with the latest build of Unity/xcode. (I'm running 4.3.4f1, with xcode 5.1.1)

Has anyone else noticed it? As I said its not a huge issue but clients have mentioned it and its quite irritating not having an answer for it.

Thanks