I had to follow the above instructions after restoring an image today.
I believe there is an official document, which probably needs to be updated. If I recall correctly, the document suggested renaming the DAT folder.
Last time when I was confronted with a similar situation, I just deleted the entire DAT folder. I tried the same today, but one item in the folder could not be removed without breaking McAfee. Anyway, I located your solution and it worked. What is also new is the need to use Safe Mode.
I'm just suggesting that the document in question needs to be updated.