Having trouble with RSS feed for search results

According to these posts:

* http://wordpress.org/support/topic/90099
* http://wordpress.org/support/topic/24861?replies=2
* http://wordpress.org/support/topic/19348?replies=2

I should be able to make the search results on my site into an RSS feed with either one of the following two URLs:

1) http://sembasics.com/feed/rss2/?s=wordpress
2) http://sembasics.com/wp-feed.php?s=wordpress
3) http://sembasics.com/wp-rss2.php?s=wordpress

However, when it doesn’t seem to be working for my site. I just get the regular feed results. Is there something that I have to do at Feedburner or on my site to get this to work?

Thanks and be well,

Moshe