Use thi file CaclsDeleteDB.exe
http://www.microsoft.com/downloads/details.aspx?FamilyID=4bc2594b-95ab-4235-b5b8-41656b38480f&DisplayLang=en
Save the file first.
After successfully running the tool.
Click update again in the onecare main screen.
If issue wont be resolved.
Run the cleanup tool for onecare
http://go.microsoft.com/fwlink/?LinkID=81699
The re-install OneCare through http://onecare.live.com
Subscribe again using your Live ID.