I'm using Drupal 6.6 at http://www.studylicense.com/drupal/ .

I'm finding that URL aliases, which don't end in a "file extension," don't work. So, whereas http://www.studylicense.com/drupal/broker.html and http://www.studylicense.com/drupal/register.php work, http://www.studylicense.com/drupal/faq and http://www.studylicense.com/drupal/user do not.

What might be causing this, and how could I fix it?

Thanks!