Mike and Serge,
I have had a USB connector come loose from the PCB after several months of use. All of a sudden, I had no COM ports just like you. The USB connector is soldered on to the PCB without any through holes to anchor it. I sent the PCB to RR so they could see the issue. This is definitely a weak area if you use the USB connector a lot.
Serge, if the unit was working fine and it suddenly does not create the virtual COM ports, I would open up the box and re-solder the USB connector. Always look for mechanical failures first. You have already ruled out the cables. The software has not changed and there is no reason to debug the computer. The RRC electronics has been rock solid for me for over 4 years without any electronic failures inside the RRC box except for the mechanical failure with the USB connector on the PCB.
Nizar K0NM