I've moved your post to the Tune-up topic folder, since this is the part of OneCare that monitors the state of AU.
Others have reported this glitch and I've occasionally experienced it, too.
When you click the "turn on" button/link offered by OneCare, does it go back to green and all is well for a while, perhaps through many reboots, or does it turn back to red for every boot-up?
Have you ignored the warning and offered link, but gone to Control Panel/Automatic Updates to verify the state of AU settings? I suspect that they are actually on, but OneCare incorrectly thinks they are off.
If the problem persists, please contact support.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve