have you tried removing the repeater and running the audio cable longer.
and is that the only USB device on that port?
repeaters cause problems alot.
also instead of the repeater you could try a small powered usb hub, as that way its generating full 5v for the usb sound card. powered usb hubs are only $20 or so. and change the usb cable from the pc at the same time as putting the hub in.