I bought a couple of 64's and they worked/work fine just taking music files (FLAC or WAV) and dragging them onto the mounted window on my Mac's desktop. Could it be the way you are working with the card? Are you plugging the C3 in to your computer directly or through a hub using a USB cord and loading up the card or are you using a card reader that is plugged into the computer? Since so many of us use 64's, I think it's more likely an issue either with how you are doing it or maybe that you need to reload the C3 firmware.
Oh, and how are you getting the files, how large are they, what format, etc?
Edited by olddude - 3/11/14 at 7:06pm