Apache/PHP performance

Hello all - I have the following server: PowerMac G4 /10.3.4 Sever/ 768MB RAM It is running Apache/PHP/Squirrelmail. I am getting painfully slow performance - like 1 minute to load the login page for squirrelmail, another minute to open an Inbox, etc. I have increased RAM - no effect, reinstalled Squirrelmail - no effect, tuned the httpd.conf file - no effect. Also, this same server ran fine when it was OS 10.1.5. Any thoughts?