A little more info:
When I restart isconfig_server with the new database info (same user/pwd credentials as the old ispconfig 2.2.18 DB), I get this:
Starting ISPConfig system...
/root/ispconfig/httpd/bin/apachectl startssl: httpd started
Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in /root/ispconfig/scripts/lib/config.inc.php on line 47
No results found!ISPConfig system is now up and running!
It appears to be running, but can't login to the admin web interface as any user, nor as admin...