The commands you listed:
Code:
zmprov ma myaccount-objectClass posixAccount .....
zmprov ma myaccount-objectClass sambaSamAccount ......
only remove the two "objectClass" entries from the LDAP entry, so removing/adding them wont accomplish too much if they are there already. They are links to the definition of that that is stored elsewhere in the LDAP schema, and since other users can log in that part isn't the issue. Unfortunately I can't think of what might be the issue if the entries in LDAP between a user that works and your user look the exact same...