Problem Summary. The default files for WordPress 2.8.4 and some previous versions, may have blank lines at the end of the WordPress system files that cause the RSS feed not to work properly.
Problem Solution. After hours of research, the following simple solution seemed to be all that was needed to fix the problem. Edit the rss.php file found in the wp-includes folder. Remove the blank line at the end of this file. The RSS feed may likely be fixed. Thanks to w3it.org and feedvalidator.org for assistance in finding this fix.