When you download your tunes from the spartan site onto your mac, it should automatically unzip them. I never have to unzip files from spartan on my mac, only on a PC. Make sure you then put your tunes in the transfer file.
Also, i have found that if you do not eject the sd card through the dashdaq prior to downloading tunes, you could have some issues. Make sure to go to the SD card menu on the dashdaq and safely eject.
I also always put the sd card(With tunes on it) in the dashdaq before i turn it on or plug it in. I have had problems with it reading the card in the past if you try to put the card in while the dashdaq is already running.