If you get an error like:
XML Parsing Error: xml declaration not at start of external entity
Line Number 1, Column 2: <?xml version=”1.0″ encoding=”utf-8″?>
When clicking the rss or atom link in your toolbox from the Recent Changes page, you probably have an extra blank line, either before the
<? php tag or after
?> tag in one of your settings files or extension files for your MediaWiki.
In my case, I found it in my EasyTimeline Timeline.php extension file. I had two blank lines at the end. Erasing those lines and re-saving the file fixed the issue.
See uncle Google for more information, but the discussion I referred to to fix my issue was here.