"Email Display As" not updating

[unHookt]

I have a Public Folder based contact list which is using a custom form. When the name of an existing Contact is modified (i.e., one of the contacts gets married and changes last name...), my users go in and change the record's last name. The record is updated and everyone can see the new name for the contact.

Now, when an email message is sent to the contact and the contact name resolves against the contact record (i.e., using "Check Names" or clicking Control+K), the person's original name is displayed.

For some reason, the "Email Display As" field does not update to correspond to the newly updated name of the person in the contact record.

Any thoughts on why this is happening?