Sometimes the screen goes completely black after exiting canon menu in movie mode. I don't have a reliable way of reproducing it yet, but it will come.
I have some thoughts though. I think it might have something to do with the fact that I normally have the screen off in photo mode. And since video mode is remapped to a photo mode, ML might sometimes think that it still is a photo mode. It doesn't happen often though. (These thought may be stupid or wrong, I just had to dump them somewhere to be able to reproduce it.)