If your PC uses an Intel Mobile Pentium processor using SpeedStep, there could be a conflict between the processor restarts and the USB sound systems need for a steady rate data stream.
NOTE: SpeedStep restarts the processor several times a second to modify its' attributes.
To workaround this behavior, turn off SpeedStep during playback:
1. Control Panel / Performance and Maintenance / Power Options.
2. Select the Power Schemes tab.
3. Select Always On and press OK.