Is the overheating problem caused - or more frequent - when capturing at 720p and 480p? That's one of the things that seems to be common about the users that have had problems. In fact, two of them seem to have subsequently found that recording at 1080p in 24 and 30fps does not have the same problem.
If that is the case, it could be due to the extra processing scaling the image down to the smaller sizes, or because of the higher frames rates (50 and 60fps) used in those two modes. Or it could be something else.