If the user is created in Systinet (not an LDAP user) then the user password is authenticated though JBOSS. Update the password for the user in the file: SYSTINET_HOME\jboss\standalone\configruation\users.properties
The format of each line is <username>=<password>
Update the line for the user and re-test. You may have to restart the JBOSS server if the file is cached.