Msg#: 3249225 posted 7:26 pm on Feb 11, 2007 (gmt 0)
Welcome to WebmasterWorld nikos. The 404 Not Found error in this instance indicates that when you upgraded WordPress you changed or removed the mod_rewrite (URL rewriting) rules which usually set the RSS feed as being under the /feed/ subdirectory.
You will probably see that your RSS feed is still available under
http://www.example.com[b]/wp-rss2.php[/b] - so you will need to re-establish the rewrite to make it work under /feed/ again.