No Sound with USB

With the usual factory pre-sets I have sound. When I plug in my USB to my computer (to use the editor or to upload user patches), my sound disappears... small 'burping' noises can be heard. I can unplug the USB, turn off the 11R, turn it back on... and zero sound. And I'm making certain that I'm selecting the correct output channel. There is nothing to be heard. I have to re-install the factory settings to get my sound back. But in the meantime, I lose any settings I may have created. Any help appreciated.