The Audio-Technica USB turntable I received for Christmas was the first thing I plugged it into my office Mac (an iMac 2 GHz Intel Core 2 Duo with 1 GB memory and Mac OS X 10.4.11) so I could start digitizing my vinyl record collection. By and large, the pair worked ok but not great. After a random period of recording a record on my Mac, the audio signal would degrade to the point of useless. Solution until today was to continuously shut down and start up again.
So, with an eye towards helping the next person avoid some of the frustration I've had, here's the workaround: Ditch the USB and go back to analog. Happily, my Audio-Technica is equipped with two 'line out' cables, one with a USB connector on the end and one with good old-fashioned RCA plugs. 'Course, if you're just recording off your RCA plugs you could have bought just any old turntable, I suppose or use the one you've got lying around in the basement.
You'll need a copy of Audacity running on your Mac. It's free open-source software. (GarageBand, which comes with your Mac will work, too, but it's a bit more cumbersome to use.) I prefer the latest stable version 1.2.6 to the 1.3 beta for this reason: When exporting the Audacity audio files into MP3 files for the iPod or AIFF files for later burning to CD, you get prompted in 1.2.6 for the artist and album title, fields which are then applied to every track/label you're exporting. In 1.3, you have to enter that information separately for every track (or maybe I just haven't read the manual close enough for 1.3).
You may need a couple of new cords as well. For info about those cords and further details, let me refer you to the instructions provided by the very helpful kozikowski . His analysis of the USB problem has the ring of truth to this former technology reporter.