Drupal recommended settings: http://drupal.org/node/270
# session.save_handler: user
# In addition, we recommend the following settings:
# session.cache_limiter: none

I had been running with:
session.save_handler = files
session.cache_limiter = nocache

I then changed those values according to: http://drupal.org/node/270
session.save_handler = user
session.cache_limiter = none

After making those changes, my Drupal web site totally broke:
-I could not login any more.
-The main page would display "na" in place of articles/nodes.

I was NOT able to get my system running again by reverting to:
session.save_handler = files
session.cache_limiter = nocache

I had to restoring the "users" database, to get the system working again.
My userid (the only one in the Drupal system) was gone from the users table ?!?!

This could be a bug (just remember this article if it happens to you and always make regular backups...).

My System at the time was:
Drupal 4.7.0Beta 3 (upgraded from Beta2)
Apache 2.2.0 on Windows 2003
PHP 5.1.2
MySQL 4.0.26 Dedicated/Different Server