I was running PD11 and upgraded to PD12 on my MacBook Air. After the upgrade, I am no longer able to mount any USB devices (may be other devices too, but I only tried USB). I am getting the "Unable to connect 'USB device name' to your virtual machine right now. Error 471". I have tried reinstalling PD12 from scratch and reinstalling Parallels Tools on my guest OS. What could be the issue? It works fine on my iMac with PD12 and OS X El Capitan. My MacBook Air has the same OS on it.