You can try the database reset tool -
http://www.microsoft.com/downloads/details.aspx?FamilyID=4bc2594b-95ab-4235-b5b8-41656b38480f&DisplayLang=en
That will cause all customizations to be lost, though, so I'd first try a simple reboot. If you use the reset tool, you will need to reconfigure anything you changed in OneCare settings and a new, full backup will be required if you are using backup.
You can also contact support if you wish -
How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
-steve
Microsoft MVP Windows Live / Windows Live OneCare, Live Mesh, & MS Security Essentials Forums Moderator