First, I'd suggest formatting the card on the mobile phone. That way, you can be sure that whatever file system the card is formatted with, it should be supported by the phone.
Secondly, when you put the card in the reader does it appear as a drive on your Mac's desktop?
You should then be dragging the MP3 song files you want onto that drive. Is that what you are doing?
- iMac G5 1.8GHZ 17" | SuperDrive | 160GB | 512MB | Airport Extreme | Bluetooth Keyboard & Mouse | Wacom Intuos II
- Pentax *ist DL - JVC MiniDV Camcorder - Airport Express - iPod Nano 1gb white