WordPress 2.1, and the FlickrRSS plugin..
Published 1 year, 6 months agoUpon installing the Gathering theme, which also “requires” the FlickrRSS Plugin.
I had received the following error on the page.
Warning: include_once(C:\Program Files\xampplite\htdocs/wp-includes/rss-functions.php) [function.include-once]: failed to open stream: No such file or directory in C:\Program Files\xampplite\htdocs\wp-content\plugins\fllickrrss\flickrrss.php on line 32
The reason for the error is, the WordPress Developers have renamed a few files in the wp-includes folder, and one of those files which was renamed was the rss-functions.php file.
The rss-functions.php file was renamed to rss.php
To fix this error, search through the flickrrss.php file to find line 32:
include_once (ABSPATH . WPINC . ‘/rss-functions.php’);
And change it to this:
include_once (ABSPATH . WPINC . ‘/rss.php’);
This should go for all those WordPress RSS plugins. Well, as far as I know… I hope this helps others! 
Also, before I forget, please feel free to add, or update your plugins on my Codex 2.1 Plugin Compatibility page!
Amos on January 6, 2007
This is good to know. Appreciate you letting us all know. I’m far away from a plugin expert but I assume bunch of plugins use the rss-function. Guess that’s a question
spencerp on January 7, 2007
You’re welcome Amos.
Yeah, from what I’m guessing, most plugins refer to the rss-function, so, hopefully plugin authors will get on the ball, and get their stuff updated soon! 
I also hope Tom, the guy that runs http://gravatar.com/ will get his site up and running again soon, so I can change this nasty Gravatar of mine sigh.
Amos on January 12, 2007
and I agree, hopefully gravatar will be up and running soon.
Ruben on February 19, 2008
Gracias por la solucion a mi problema. Encontre en un primer momento a que se debia, pero no queria renombrar el archivo… traduje el articulo y lo publique en mi blog.
Saludos.
(Im sorry, my english is bad…)