I believe the NEX can either produce AVCHD or AVI?. The AVI should be viewable by anything. AVCHD is a bit more finicky. Do you have a NEX3 or 5? If a 3, I think AVI is the only option. If NEX5, you might be able to set it to use AVI instead of AVCHD.
Try this, though, on your iMac. Plug the SD card into your imac, and launch iMovie. Then select "import from camera." If it is AVCHD, the SD card will mount like a camera in iMovie, and then you can choose to either archive, which copies the files to disk for later, and then you can delete them off your card, or import them direct into iMovie for editing.