I know about a dozen or so people who own a GoPro Hero 3 - Black Edition
and all but one of them ran into some kind of problem with it, the most annoying being that it would lock up completely and the battery would have to be removed to reset it (What a pain).
Turns out, that when you first get it, you will be instructed to perform a "firmware update".
There are 2 ways to perform the update;
1. Automatically, through Java Script while your camera is connected to your computer.
2. Manually, download the update to a micro SD card, insert into your GPH3, and then turn on.
Through a little bit of research, my understanding is that if you update your firmware with the auto installer, you will run into all kinds of bugs and issues. This is also confirmed on an Amazon Review:
Go Pro Hero 3 Fix | Amazon Review
I updated mine manually, and the only issue I had was the preview wasn't working that great on my iPhone at first, but after turning everything off and reconnecting, everything is working fine now and I am not having any issues at all.