Just noticed something today after the problems persisted even after the move to Feedburner. This is the first time I've noticed this behavior, but the problem has always be a little intermittent, so who knows.
The first time I posted an item, it looked like this (only posting the relevant parts):
<item>
<link>http://slashstar.com/blogs/tim/archive/2005/06/16/I\_have\_Tablet\_Envy.aspx</link>
<comments>http://slashstar.com/blogs/tim/comments/1920.aspx</comments>
<wfw:commentRss>http://slashstar.com/blogs/tim/commentrss.aspx?PostID=1920</wfw:commentRss>
<description> ... <img src="[http://slashstar.com/aggbug.aspx?PostID=1920](/aggbug.aspx?PostID=1920)" width="1" height="1"></description>
</item>
<item>
When I post the next item, it gets published like this:
<item>
<link>http://www.slashstar.com/blogs/tim/archive/2005/06/16/I\_have\_Tablet\_Envy.aspx</link>
<comments>http://www.slashstar.com/blogs/tim/comments/1920.aspx</comments>
<wfw:commentRss>http://www.slashstar.com/blogs/tim/commentrss.aspx?PostID=1920</wfw:commentRss>
<description> ... <img src="[http://www.slashstar.com/aggbug.aspx?PostID=1920](http://www.slashstar.com/aggbug.aspx?PostID=1920)" width="1" height="1"></description>
</item>
Ooops. Notice that the description and all those other links include the www. in the second fetch. In both cases, I'm accessing the feed through the same URL.
The first thing that comes to mind: it looks the URLs in the RSS feed are determined dynamically with a call to SiteURLs. It looks like SiteUrls uses relative URLs. Could it be that, depending on how I access the site last (either the blogs or the admin) determines the base URL to be used when building up the RSS to be cached?
I've posted this to the Community Server forums, but I'll keep digging. If anyone else has any ideas/thoughts or has run into something similar, please let me know!