Background:
This is a clean 4.6 install (from scratch) that was successfully configured and tested on a sandbox apache installation without incident.
My server is running php 4.3.11, mySQL 3.23.49 on the typical apache 1.3.33 linux box; it's a very vanilla CPanel style server, I installed phpmyadmin and imported my database without thinking twice about it (I've been doing this long enough that I should have been able to get this running in my sleep, ergo I am REALLY beating my head against the wall to get this working, now).
Under sites/default/settings.php I have:
$db_url = 'mysql://atlasiss_dbuser:mypassword@localhost/atlasiss_lbiw';
$db_prefix = '';
$base_url = 'http://www.atlasisshrugging.org/lbiw';
(And for the sake of acknowledging my own technically illiterate paranoia, I chmodded everything to 777, to see if this would appease the Powers That Be. It didn't.)
I can validate that these are correct as if I remove CPanel's funky little prefix (and we've all seen them), I'm rewarded with:
Warning: mysql_connect(): Access denied for user: 'dbuser@localhost' (Using password: YES) in /home/atlasiss/public_html/lbiw/includes/database.mysql.inc on line 31
Access denied for user: 'dbuser@localhost' (Using password: YES)
leaving me a momentary sense of nostalgia since, were that the error, I could fix it.
Last but not least, I have verified that localhost is, indeed the correct server for mySQL, and scanned the logs for useful errors which contain nothing but mentions of traffic from robots and my abortive attempts to do things like open index.php directly, etc.