"Your PC Needs to be repaired" on startup

Win 8.1 Pro x64. What started as a failed update from Comodo CIS 7 to 8 free this morning has step by step turned into an immediate startup error: Recovery - "Your PC needs to be repaired." The file indicated is \system32\winload.exe, error code 0xc0000225. Another version is "A requied device isn't connected or can't be accessed. Error code 0xc000000f." When I press F9 for another OS, it shows the first error code. What immediately preceded this was setting up a safe mode startup, so I could try a different way of dealing with the problems that had developed. At the time, it struck me that the startup choices/layout in msconfig looked like the old one, not the one I had seen in 8.1, but maybe Windows had changed it. In any case...

I've tried booting to the original Win 8 CD and going into Repair>Troubleshoot>Advanced. The problem there with System Restore is it can't find an offline boot volume (I checked the SSD's connections, however unlikely that was). In addition, Automatic Repair fails, and System Image doesn't see any (one on another drive, but it's nearly three months old).

Suggestions?

Update: I've run the following from the command prompt, taken from Solution to your PC needs to be repaired Error code: 0xc0000225. It worked. Now I can deal with the other problems (another post soon).

Diskpart
List volume
Select volume=2 (replace “2” with the number that is associated with the “ESP” label)
assign letter=Z
exit
bcdboot C:\windows /s Z: /f UEFI (replace C: with the volume letter that is named “OS”)

Haven't succeeded yet. The first problem is in list volume: C shows as the system reserve, while J seems to be the right size and shows as "Windows 8 Dr." But nothing is labeled "OS" in the list volume info column (it's all blank) and neither J nor C are working in the bcdboot step (the system drive is an SSD and is running UEFI). Not sure what I'm missing.

UPDATE 2: Solved it with this: How to Fix Winload.exe Issue in Windows 8, 8.1