You will find the USB Selective Suspend settings in the Advanced Options for Power Management Options.
By default, Windows will sever connection to a USB device, after some period of time, to conserve power. When this happens, Sonar does not react well, so most folks go into Power Management Options, then to the Advanced options, and within those options there is a setting to tell Windows to allow or not allow the USB Selective Suspend behavior.
Hope that helps,
Bob Bone