Three issues seem to have happened at the same time.
One is that the GRUB countdown timer doesn't exist anymore. I had set to 30 seconds.
Second is that there's now a GUI GRUB screen instead of text.
Thirdly, USB ports seem to have stopped working. I've tried two KBs in multiple ports and I can't even get to the BIOS setup. Booting from a CD is similarly useless
The disappeared GRUB countdown means that it won't boot at all so I can't even ssh in.