Hi Chi,
to unset the flag you have to do the following steps carefully:
1. Search the dataset in the DB:
SELECT portalPreferencesId, ownerId, ownerType, preferences
FROM PortalPreferences
WHERE (preferences LIKE '%eiamadmin%')
2. Manipulate the entry: change from true to false
<preference><name>eem.authentication.enabled</name><value>true</value></preference>
3. Restart CA Unified self-Service Server
After that you can login as CASMAdmin against USS_mdb-user
Regards,
Peter
PS.: To be sure save USS_mdb before doing that