You need to make the address record be seen as yours in Address Book. The link below is for a previous version of Address Book, but it works the same in Lion.
I have a similar issue with a slight twist.
I have 'My Card' setup properly, however, I do have 5 email addresses that I use and these are listed on 'My Card'. When I select the option to add an email alert on a calendar event, the app is picking up two addresses from the set of 5 and makes me pick one.
I would like to select one of the other addresses to be the default for sending out the alerts. Is there a way to do that. If it is helpful, the app is picking up 2 of the 'Work' email addresses. I don't know if the home vs work designation would make a difference.
Note: I am looking for a solution to pick one a specific address from the contact card to send out the alert email. I am NOT looking to have a discussion as to why I have 5 addresses.