Check this list
- mod_rewrite enabled in the Apache conf file
- AllowOverride enabled in the Apache conf or vhosts file (so that
.htaccess rules can apply)
- The .htaccess filename specified in the Apache conf file
- An .htaccess file in the root of the Drupal directory (may be hidden
on some filesystems, but should be there)
- Rewrite instructions in .htaccess (distributed with Drupal, but
sometimes needing tweaking)
To test your settings, run
apache2ctl -t
apache2ctl restart
read this also - http://drupal.org/node/15365
Regards
*vivek r
vivek.fossis.org*