To isolate the computer voltage, GND and data lines from the X2, i insert a USB-Isolator between my iMac and the X2. It is a small pcb from Circuits@Home and based on the Analog Devices ADuM4160 USB Isolator IC.

Because i want to use the best power solution, i ordered the "Isolator only"-Kit and connected the downlink side to the +5V Salas Shunt module, witch powered now the X2 over the USB plug.