It would appear that you do need to reinstall since you are encountering errors that should not be happening, but normally, you do not need to reinstall to renew. OneCare updates itself as long as your subscription is active. If you purchase a new retail copy for renewal purposes, simply sign into http://billing.microsoft.com with the subscription LiveID and select Renew for the OneCare subscription and use the option to renew with a PIN/Key.
-steve