I assume that you have seen and followed the steps here:
Information to help troubleshoot and resolve update problems -
http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=1286736&SiteID=2
If none of that helps, please contact support.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2