I use Squared 5 - MPEG Streamclip video converter for Mac and Windows for the mac, as good as it gets and free
Often the updates for itunes will kill any codecs and you need to start again. Apple like to do clean installs for strange reasons
New firmware came out today, updates some of the issues and adds new features...
I tested it and it works well.
Go to the gopro site under support to get the file, easy to do..