To get a working connection between your phone and mac use this trick:

connect usb cable to phone
press voice command button
connect usb cable to computer

You can then hit home so you dont have to worry about voice command doing anything you dont want it to do. Now you can transfer mp3s pictures etc etc.
If for some reason it doesn’t work try this: turn your phone off. remove the battery and leave it out for 1 minute. then …