Hey Me and my work mates have figured out how to get the touch working for anything using iOS Retna scan. Basically for some reason the screens think they are twice the size of what they actually are. So you have to divide it by two. For an example we had a menu system that wasn't working for iPad 3 or iPhone 4 so what we did was:
1)We created an event which was 'Touch Start' added another condition to the event which was systems - Between Values them in 'value' type in: Touch.X*0.5 'Lower bound' type in: Sprite_Button.X - (Sprite_button.Width*0.5) 'Upper bound' type in: Sprite_Button.X + (Sprite_button.Width*0.5)
2)We then added another Condition which was the same as above Systems - Between Values.
In 'Value' type: Touch.Y*0.5 'Lower Bound' type:Sprite_Button.Y - (Sprite_Button.Height*0.5) 'Upper Bound' type in: Sprite_Button.Y + (Sprite_Button.Height*0.5)
Overall in that event there should be 3 conditions in there. So when the player touches with in that area then it will do what ever actions you have programmed. Hope that helps you.