$base_url and the mystery of broken feed images I recently upgrade my Drupal6 site to Drupal7 and migrated to getpantheon platform, I am hand-coding absolute image url's in nodes like this :

&lt;div align="center"&gt;
&lt;img src="http://www.megaleecher.net/sites/default/files/images/sneaksy.jpg"
style="max-width:100%;height:auto" alt="sneaksy" /&gt;
&lt;/div&gt;


Despite using full absolute url's, images in feedburner are getting broken : http://feeds.feedburner.com/TheBestInternetNews as it's source http://www.megaleecher.net/rss.xml is outputting relative images. 

Strangly, using $base_url = 'http://megaleecher.net'; (without www) in settings.php fixes the issue but using $base_url = 'http://www.megaleecher.net'; (with www) makes them relative again.

I have hired two drupal dev's from oDesk (https://www.odesk.com/o/jobs/job/Fixing-relative-image-paths-Drupal-rss-feed_~~0c48e61824bc3263/) and also asked for support from getpantheon but no solution.
Module Pathologic might help your problem, if you haven't tried that. Here is a quote about it (from the module's project page):

... is an input filter which can correct paths in links and images in your Drupal content in situations which would otherwise cause them to “break;” for example, if the URL of the site changes, or the content was moved to a different server. Pathologic can also solve the problem of missing images and broken links in your site’s RSS feeds.
Pathologic is designed to be a simple, set-it-and-forget-it utility. You don't need to enter any special “tags,” path prefixes, or other non-content noise into your content to trigger Pathologic to work; it finds paths it can manage in your content automatically.