Do you have the 3.5 inch digi drive with it?
Edit: You mentioned it by saying USB...
Here is what I found on there site.
Due to data transfer limitations of the USB 1.1 connection, it may not be possible to play back, record or simultaneously record and play back content at the highest bit rate and/or frequency supported.
2.1 speakers:
Creative Inspire T2900
Creative I-Trigue 3200
Creative I-Trigue 3300
Creative I-Trigue i3350
Creative I-Trigue 3400
Creative I-Trigue L3450
Creative I-Trigue L3500
Creative I-Trigue 3600
5.1 speakers:
Creative Inspire P580
Creative Inspire P5800
Creative Inspire T5400
Creative Inspire T5900
Creative I-Trigue 5600