During Friday evening, I was busy enjoying my new 7D, taking some photos with the built-in flash. At one point, I became aware that this pop-up flash would not stay down. I spent the next 24 hrs agonizing over what was wrong! I read the book, checked online and no other instances of this malfunction came to light. Desperate, my wife suggested that I attach my Speedlite to the hotshoe...
I took a few photos with Speedlite attached, then dismounted it, pressed the popup flash release button and, hey presto, the retaining lugs were released to the normal position and now the popup flash behaves, well, normally. I came to the conclusion there was a software/firmware glitch, which has now rectified itself, and the camera is once more my best friend...
For your reference, or discussion.
I've seen other problems with the pop-ups. One I personally helped with was that the pop-up would NOT fire, regardless of how the settings were configured.
The fix for it was the press the camera's reset button. This wasn't a Nikon or Canon camera. I don't remember what manufacture is was, but it did have a reset button.