How to change my RSS feed url?

My RSS feed is still not working on http://www.thegreenriderules.com. I think the reason is that when I click on RSS (in browser address bar) it includes the www. In my other blog (a wordpress.com) it does not have the www in the feed and works fine. I thought this was automatically generated, so I don’t understand why I should have to change it, but I am grasping at straws here. Please tell me where this URL is determined and if it can be changed. THANKS!