I recently got a US428 to use with Sonar 2.0. It looks like everything is working correctly but I don't get any sound from my headphones. I plug in my guitar and the input LED's light and sound wave show up on the screen but I can't hear anything. I don't have monitors yet so I have not been able to check through anything but headphones. I tried to use the bundled Cubasis as well and I had the same problem. Any thoughts?