This error means that there is a problem with the Windows Installer. See if the link at the end of this thread helps:
http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=3693261&SiteID=2
If not, please contact OneCare support.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve