Hey wow, the Error has disappeared! My bad, my cat5 mustn't have been seated securely! I was booting with a controller then switching to the pcb once games have loaded, but it's now succeeding at boot
Here's the PCB, it supports a bunch of retro consoles via cat5
https://paradisearcadeshop.com/fgc-cons ... hulhu.html
The new model had a pre-order with onboard Ethernet (finally) and physical compatibility with popular arcade sticks, shipping Dec 2016.
EDIT: well now I'm getting Error Code 80000014 on boot if it's plugged in, so I guess I was half-right. Disconnecting and reconnecting fixes it.