I finally got it to work. What a nightmare.
First, you have to add a USB Device filter in the VirtualBox preferences. I added one for the device, and got the firmware updater to recognize it, but then when the device was being updated by the software the device info changed, and it was no longer recognized.
I figured, finally, I could add a device filter with just the manufacturer name "Fanatec" and it would recognize the wheel every time.
Then I tried flashing with an XP VM. That never got past "resetting Fanatec wheel as commport". I got it to finally work in a Windows 8 VM, although the first time through it froze in the middle of "Flashing...." and I had to restart, and hold my breath.
But it's working now. No more freezing in the game. Now I just need to get settings working!