Unity stops rendering

Hey all, seeking some wisdom, ideas, anything.

I acknowledge that the info I provide here is vague but it's all I have and I'm desperate.

I have a production iOS game that calls out to a third party SDK and they draw over our game with their own UI, we have a bug/issue where sometimes (less than 1 in 100 times) where upon return to our game the rendering ceases. We load a different scene and everything appears to work except nothing is rendered to the screen - the screen is left with the content from the previous scene (which happens to be a black blank screen) any ideas on what might be going wrong?

The process is:

1) Load empty scene that has 1 camera and a delegate object to receive callbacks from the third party SDK.

2) Call third party SDK - this draws their own UI (native iOS, not Unity) they do something with UIControllers or something to draw over our game.

3) Thrid party SDK calls back to our delegate (in the empty scene) we then load the next correct game scene.

4) Game scene loads but nothing renders - it's still showing the empty scene's content (we set the blank scene's camera's background to 0,2,0 so we can identify what is left rendered on the screen).

5) Although nothing is rendered the game runs properly (we can interact with it and hear the correct things happening - touch events are functioning etc) so we know we loaded the scene correctly.

I'm totally at a loss how to start addressing this. Any ideas, hints, etc would be greatly appreciated.

Using: Unity 4.5.5p5, also happens with 4.5.5f1