Flashing 'H' in the middle of the movie

I saw this in 3D, and several times in the middle of the movie, a large, blocky, capital H appeared on the screen for an instant (probably 1/24 of a second or less). It was in the right half of the screen. I couldn't figure out, was this some kind of antipiracy scheme, or if not that, then what? Just a technical glitch? I've never seen it on any other movie.