Sticky email alert in iCal event.

[Whitehill]

I'm trying to retire an email address. Among other things, I have changed all existing iCal items that send email alerts to use a new address. However, the change doesn't take effect. Sitting here just a couple of minutes ago, I watched one trigger and send a message to the old address. I immediately double-clicked on the item and, sure enough, it had the new address listed. Am I missing a step?

BTW, this has been going on for weeks.