I have the same problem after updating the BIOS on my Crosshair Hero VII to 2901 AGESA 1.0.0.3, but at least I now know that the blinking light is the scroll lock light.
I didn't know what it was at first.
The Windows lock key and F1 trick helped, but then I have to reinstall the USB driver for the kbd on every boot.
My initial problem was not being able to get into the BIOS, which is pretty fundamental.
Is there a fix for this?