Check if the date and time setting of your computer is correct.
Save and run this tool.
CaclsDeleteDB tool. Updating Virus and Spyware Protection Fails
http://www.microsoft.com/downloads/details.aspx?FamilyID=4bc2594b-95ab-4235-b5b8-41656b38480f&DisplayLang=en
Anti-Malware repair tool. This tool will attempt to repair the virus and spyware protection component of OneCare on your computer.
http://www.microsoft.com/downloads/details.aspx?FamilyID=70adca25-950c-4b1b-a5e2-297e80aa67b1&DisplayLang=en
If you're using a Vista OS, make sure to go to the location where the file is saved, right click on the file, choose run as administrator.
If both file won't resolve the problem, contact support.
How to reach support (FAQ) -
http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2