My 15Gb £rd Gen iPod isn't being recognised by my iMac. The firewire cable is working as it charges but if I connect through USB nothing happens on either iPod or iMac. I've reset the iPod a few times (Play and Menu right?, it scarmbles the screen and then comes back on normally) and tried with various firewire ports and usb ports. What's gone wrong and how do I fix it? Cheers for any help.