Well, this seems to be rather common now. My one R4 B2 that's been running for 4 weeks had one board stop working yesterday. After reading here that it's been happening to others and that some have gotten it working again by updating the firmware, I tried that also. Firmware update seemed to go fine, but only 1 board working still and after the firmware update the other board seems to be working but it's showing a large number of total HW errors even though the working board errors are almost none. Now what?
I would disconnect the INOP board and hopefully you see less HW on the other board. I can't prove this but I would suspect keeping power going to the INOP board may further damage it.
I am sending one of my broken R4's to Denver and will keep everyone posted on turn around time. I have one other that needs repair that I might send to Hong Kong.