Really odd Domino BES behaviour
Read the whole thread as it will help you to understand the issues here, but in a nutshell:
From you original post, I am assuming that this user-in-question is NOT an iNotes or a roaming-profile user.
Chances are they have a profile document present in the mailbox called "inotesprofile".
That profile gets created if anyone ever uses the Action - Synchronize Address Book agent in the mailfile. There might be other ways for that profile to get created, but that's the one most likely.
If they are not setup properly for iNotes, but have this profile in mailfile, BES is effectively looking for something that doesn't exist in terms of address book config.
You have 2 options:
a) delete the dodgy profile doc from user mailfile, delete user from BES, re-add, re EA, all good.
b) change a registry version on the server to stop these fields from auto-populating. Plus side, don't have to do (a). Downside, you have to manually populate new user fields on BES, even for roamers etc.