Mine froze once in the middle of a Sonic Racing Transformed race, with a really annoying high pitched sound. That's the only time it's happened to me, but it's been confirmed that this is related to Miiverse and doesn't happen if you're not online or haven't updated. Nintendo will probably fix it once they figure out what the issue is, but something like this could be hard to track down.
However if that BIKER_BOB guy is right the issue is not within Miiverse itself, but Miiverse could be triggering it.