Here is the error I get when starting ISPconfig:
[root@mail ~]# /etc/rc.d/init.d/ispconfig_server restart
Shutting down ISPConfig system...
/root/ispconfig/httpd/bin/apachectl stop: httpd stopped
ISPConfig system stopped!
Starting ISPConfig system...
Syntax error on line 205 of /root/ispconfig/httpd/conf/httpd.conf:
Cannot load /root/ispconfig/httpd/libexec/libphp5.so into server: libmysqlclient.so.14: cannot open shared object file: No such file or directory
/root/ispconfig/httpd/bin/apachectl startssl: httpd could not be started
/root/ispconfig/php/php: error while loading shared libraries: libmysqlclient.so.14: cannot open shared object file: No such file or directory
ISPConfig system is now up and running!
I upgraded the server to php5 (centos). Not sure if this would have anything to do with this error.