I use the new driver with the UR22 and Mavericks. With 1.8.3 there ist no sound with VLC-Player and sometimes iTunes is also muted. By using the intern MacBook Pro Sound everything works fine. I downgraded to version 1.8.1. But with 1.8.1 I have Kernel Panics every day. Please Steinberg-Programmers: make a working driver for UR22 with OSX-Mavericks!!!