What version of PHP/MySQL?
Per the d.o. requirements page, D6's requirements are:


Web server: Apache, Nginx, or Microsoft IIS
Database: MySQL 4.1 or higher, PostgreSQL 7.1,
PHP: PHP 5.x only (5.2.5 or higher recommended). Warning: support for PHP 4.x has been dropped. Drupal core should work with PHP 5.3.x, but PHP 5.3.x and higher may produce errors or unexpected behavior especially for contributed modules and themes.