this is primarily an iphoto isssue. I view and see all of my files in iphoto.
all videos originally imprted and played in iphoto, until I changed video settings to PSH AVCD from FSH AVCD.
the unreadable files are shown as the MTS files and others files:
but the video content on the camera shows a (non-folder) called private. with no further breakdown. and does not recognise that anything further on the camera is available for download
I'm sure that some software came with your camera that will process these and can export them to a supported format.
A note on AVCHD: This format was developed for people who are shooting to edit the material afterwards. If you're shooting to edit, then iMovie or Final Cut are the correct home for this material. If you're not shooting to edit consider using one of the other video formats on your Camera.