first time startup fail

Hello,

Upon first connection to my first, shiny, fresh, new drupal install I am,
sadly greeted with:

Fatal error: Call to undefined function session_set_save_handler() in
/var/www/localhost/htdocs/drupal/includes/session.inc on line 9

Here's a few system particulars:

uname -a
Linux goliath 2.6.12-gentoo-r10 #5 SMP Wed Oct 26 20:07:32 PDT 2005 i686
Intel(R) Pentium(R) 4 CPU 3.40GHz GenuineIntel GNU/Linux

drupal: www-apps/drupal-4.6.5
php: dev-lang/php-5.0.5-r5
apache: net-www/apache-2.0.55-r1
db: dev-db/postgresql-8.0.4

Any help will be most appreciated!

Thanks,

-al