Last time I tried there were HTTP and RTMP MP3 audio streams at MySpace. HTTP streams can be recorded with many programs. You may try VLC or MPlayer, for example. The only problem is to get URLs of these streams. You may try some packet sniffers.

The only software I know that can record RTMP MP3 streams from MySpace is Replay Media Catcher for Windows. To run it on an Intel based Mac you'll need something like Bootcamp or Parallels Desktop for Max OS X.