Starting from version 7.0, users with duplicate logins are not allowed in BA database. This inconsistency may cause trouble during upgrade to BA 7.0.
Run the following query in BA database console:
~ pba=> select "Login", count(*) from "IntUsers" group by "Login" having count(*) > 1;
It will show you all duplicated logins. To get details of those users, run another query
~ pba=> select * from "IntUsers" where "Login"='found_login';
Change logins of these users prior to upgrade to 7.0.
To update a user with new login, run
~ pba=> update "IntUsers" set "Login"='new_login' WHERE "UsersID"='found_user_id';