Let me start with: I'm really impressed with this plugin and the community and author support I see here. Thanks so much for the great work--not an easy job.
I just started trying to use MaxCDN to cache my static files today. I'm using it with 3 blogs. On two sites, the URL substitution appears to be broken--it looks like it's dropping off everything but the MaxCDN "replaces site hostname" for many of the image URL's. All sites are running the latest version of WordPress and the plugin
Here is an example page that I've made up that has both relative and absolute full URL's in place for testing. In this case the full URL works, but none of the relative URL's do.
You can see this page (with debug on for CDN) here at least for the time being: http://www.185vfx.com/2012/01/dinner-tim/
Here is the debug from the bottom of that page so you can see the broken substitutions:
Replaced URLs: /images/2012/01/dinner-time-800x533.jpg => http://static.185vfx.com/ /images/2012/01/dinner-time.jpg => http://static.185vfx.com/ /images/2012/01/dinner-time-480x320.jpg => http://static.185vfx.com/ http://www.185vfx.com/wp-includes/css/admin-bar.css => http://static.185vfx.com/wp-includes/css/admin-bar.css http://www.185vfx.com/wp-includes/js/admin-bar.js => http://static.185vfx.com/wp-includes/js/admin-bar.js http://www.185vfx.com/wp-content/themes/autofocus-rob/style.css => http://static.185vfx.com/wp-content/themes/autofocus-rob/style.css http://www.185vfx.com/wp-content/plugins/picasa-album-uploader/picasa-album-uploader.css => http://static.185vfx.com/wp-content/plugins/picasa-album-uploader/picasa-album-uploader.css http://www.185vfx.com/wp-content/plugins/dd-formmailer/dd-formmailer.css => http://static.185vfx.com/wp-content/plugins/dd-formmailer/dd-formmailer.css http://www.185vfx.com/wp-content/plugins/dd-formmailer/date_chooser.js => http://static.185vfx.com/wp-content/plugins/dd-formmailer/date_chooser.js http://www.185vfx.com/images => http://static.185vfx.com/images
I setup a 3rd fresh wordpress site for testing and although it has fewer images, it appears to be working exactly as expected. I'm not sure if it's related to the quantity of images or something else in the HTML that might be throwing off a regex expression.
I'm open to any input and hopefully can provide useful debugging info. I've also submitted a support ticket to the plugin author just in case that helps.