Hi
If you have the latest Mac OS it kills the compatibility to read AVCHD files directly from your camera card.
A free way to read your files is to create a script that opens the single big PRIVATE folder so you can see each of the files.
But Christiano's method is really good. See the link below.
http://cristianogiardina.com/quickly-access-your-avchd-files-in-mountain-lion/
Cheers Clay