According to Natsume there are a few known bugs with HM. The game tends to freeze when it gets hot(this happens after about 2 hours of game play), and it seems there is no solution to this bug. The other is the freeze-up that occurs when too many things are moving on screen at one time.
Although I have HM myself, and have had NO problems with freeze-ups…I have heard of this from other gamers.
Oh well…what ya' gonna' do??