Access Denied Error for Drupal 'update.php' page

To be honest, I feel rather foolish. This is a problem I've been having with Drupal on and off: I click on the 'Run Updates' menu item in the Adminstration Menu and every now and then I get an access denied error. Since I have access to the server, I was changing the settings.php/update.php file to allow me access to run update.php (see here: Running Update.php). This was annoying me, but it only happened occasionally, so I lived with it.

Today, I figured out what the problem was. I don't use the 'www.' in front of most of the sites I visit, and I would pretty much never type it into my browser. Assuming that the server on the far end is configured correctly, this is not a problem (the few times it doesn't work, it annoys me, an irrationally large amount). When I visit my own sites, I don't use the 'www.' either. When I login as the admin for my sites, I still do not have the 'www.' in front of the domain name. The problem is, Drupal authentication treats 'www.example.com' as a different domain from 'example.com'. This means, if I login as user 1 while at 'eoinbailey.com' but try to run 'www.eoinbailey.com/update.php' I will receive an access denied error.

If you delete (or add) 'www.' from the front of the domain name, you will have your access again. PROBLEM SOLVED!