I did answer that post, I thought.
I have had the same problem a few times on a few of my PCs in recent weeks, the most recent being yesterday upon rebooting the second time for the install of the February security patches that were downloaded via Automatic Updates. When I logged on, I got the at risk warning and it was telling me AU was off. Clicking the button in the warning made it go away. I don't know what causes it, but I remember from your other post that you said it happened every few days on your PC.
I don't have a solution for you, but apparently this is not an uncommon problem. You may want to contact support, but I do believe that you are turning AU on. Whether OneCare loses track of this or if AU somehow is turning off, I don't know.
-steve