Quoted from LTG:Turn off. Try again. If it hangs again use the USB stick method.
LTG : )
Thanks for the fast reply, as usual
So I gave on the network after trying it a few times. I've now also tried:
1. USB delta update method - twice, with different size/speed USB sticks
2. USB full upgrade method - three times, with different size/speed USB sticks. Once using a windows machine to create the image, once with a Mac, and roofus and unetbootin. All get to "mounting /dev/usb" but then eventually boot into the game code instead of the updater. However, once it's in the normal bootloader it's too late for the full install anyway.
On a whim, I created a virtual machine on parallels and booted the image ... and it works. So the USB stick is good. Is there a chance the BIOS on the machine isn't set with USB as priority? I tried to test that theory by connecting a keyboard, but I can't get into the BIOS as it is password protected. I'm sure there is a jumper somewhere where I could reset everything and get past it, but that seems a bit extreme.
EDIT: I also tried a different USB port with the same results.
Any suggestions?