Pretty Permalinks not working – Resulting in 404

I am running 14 different self-hosted WordPress installations using a mac server. My IT guy kindly set up another webroot for me, as he has done the 14 times previous, and for some reason with this installation, I cannot get pretty permalinks working.

I have created the .htaccess file and have pasted in the code generated by WP:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

I have saved the default permalink structure, and then switched to the alternate structure that I wanted. Any other structure aside from default results in a 404.

I am currently using a default WP theme, and no plugins.

I parsed the contents of the following into a file in my webroot to verify that mod-rewrite is enabled. It is.
<?php foreach( apache_get_modules() as $module ) echo "$module<br />"; ?>

I have deleted and recreated the .htaccess file numerous times, changed the permissions from 644 to 666 so that it could be written to, and then changed the permissions back. I have tried specifying the category base and the tag base (not leaving those fields blank).

I even deleted everything in my webroot, and reinstalled WP.

I just don’t know what to try next. I have been tasked with creating a closed community networking site by the middle of August and need to have the pretty permalinks working to use BuddyPress. Perhaps BuddyPress isn’t the best solution, but I won’t know until I can get the permalinks working correctly.

Any advice or suggestions would be greatly appreciated.