It appears that there is a problem with that update on your PC. OneCare simply reports that the update is being offered and not installed and then directs you to Windows Update, it does not update Windows for you. Try the Windows Update Solution Center -
http://support.microsoft.com/ph/6527
Or you can contact OneCare support -
How to reach support - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
If it fails to validate your subscription, select the option that you are using a trial or beta copy and you can proceed to email support without validation once you've signed in.
-steve