If you can't login to the WiKIDAdmin site due to a bad username and password, there is probably an issue with database connectivity. Check that postgres is running on the proper port:

netstat -anp | grep 5432

Check that 127.0.0.1 is the first item in /etc/hosts and not the IPv6 ::1 listing. (Though this seems to be less of an issue with 3.0)

Make sure that postgresql-jdbc is installed.

Disable SELinux.

Check that the pg_hba.conf file copied properly:

diff /opt/WiKID/conf/templates/pg_hba.conf and /var/lib/pgsql/data/pg_hba.conf

If you get any response to this commmand, it may be that you didn't run this command:

/opt/WiKID/sbin/wikidserver_config.sh

Or that you did not reboot or run this command:

/opt/WiKID/conf/templates/wikid-firstboot.sh