I cannot delete several of my messenger contacts even though i deleted from my mail address book. when I try to delete them, I get the following error message: The last Address Book operation did not succeed due to a server error (Error Code: -40402).

Seems Error Code 40402 pops up when trying to remove them while in your Yahoo Instant Messenger list first.

Glitches and Updates!!! Here's a work around though.
You will need to go to your Yahoo Email Account and delete the contact's name there first.
1. Click Contacts from your Email page to open your list of Contacts.
2. Go to the one you wish to remove and check the box next to it.
3. Go to the top of the list and click the Delete button.

Go to Yahoo Instant Messenger, right click the name and select Delete from the drop down menu.