I was fighting through the same issue my my Spider a few days ago and came across a post that suggested using a different Gadgeteer cable between the board and power. It worked for me after trying three different cables.
I once had an similar issue.
The cause was that I had an USB serial module to my MedusaMini connected at the same time.
By this FEZConfig could not find the Cobra II in booter mode.
I’d guess it was talking to the Medusa.
SO if you have any other USB Serial device connected to your computer this might be the reason it is not working.
@ njbuch - We were finally able to get the code 10 error a few others have reported, but only sometimes, only on a USB 3 port, and only on one computer. Once we switched to USB 2, the error has yet to present itself. I would try to find a USB 2 port to use if you aren’t already as we don’t currently have a fix for the USB 3 issue we saw.
I’ve been experiencing problems here too and @ Andre.m suggested that the USB_DP should be powered too, not just rely on the power from the USB port. I haven’t tried it on my Spider yet, but seeing as I has Windows 8.1, I let you know once I have.