Its not a USB issue...Its the same glassy howl whether my laptop is connected or not, even on stage. Ive tried the steps above and have "lowered" the irritating noise somewhat, but its still there. Im not being picky either, the other guitarist on the other side can hear it between songs. I have plugged both the amp and POD into the same power conditioner, plugged them in to different areas, replaced cords, just about everything I can think of. One difference I did notice last night was that it "pretty much" goes away when using my CLEAN channel of my amp (its still there but much less noticeable). This is with just delay or maybe reverb on the POD. It increases dramatically when switching my AMP to the gain channel.