Can anyone else with a Canon 60D try this to see if this happens to them, please.
After using any flash unit the built in flash unit does'nt pop up any more. The menu system reports that an external flash is still present.
Under the left rail guide on the hot shoe there is a very small micro switch that get pressed down by any hot show mount telling the camera that an ext flash is mounted. You need to gently lift up the spring to release the switch again.
I can already hear the Nikon guys laughing.