I moved your post out of the archive folder for the antivirus topic.
It would appear that the update may be failing to install properly or that it isn't registering itself completely.
You can contact OneCare support -
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
But a better path would be to look at the support options for Windows Updates -
Windows Update Solution Center - http://support.microsoft.com/ph/6527
Finally, the date in Add/Remove programs does not reflect the usage of the actual program. As long as your OneCare icon in the system tray appears, it is running.
-steve