I was passing nvidia card and usb keyboard and mouse to vm. I changed that today back to unraid. To do so I edited the vm removing the devices.  Then I installed nvidia driver. Then I changed the immou pass through setting in vm to not individualize the groups. Upon reboot i get stuck at usb portion. The usb devices get registered and then it says xhci_hcd 0000:02:00.0: usb bus 1 deregistered. The lights on my usb keyboard And mouse turn off and the boot process never completes. I went into the flash backup and attempted a restore and no change. I restored the vfio configuration file to the backup one. No change.  Apart from starting over on my build, what is the next step?  I also added an additional usb mouse and keyboard. When I put them on the ports on the top of the computer their lights went out too. When I plugged them into the mother board the lights stay on but the boot is still stuck. 

Try deleting/renaming /config/vfio-pci.cfg on the flash drive.

That did the trick. I forgot to unattach the usb devices from the VM prior to the reboot.