For some time I’ve had people asking me why they get that “an error has occurred” message so frequently with KB Advanced RSS. I have figured out that it is definitely not an issue with my widget, since people get the same error when I tell them to try the default RSS widget. But while browsing the WordPress support forums recently, I came across a thread that may explain why so many people get this error: Their hosts are restricting the site from requesting the feed.
I’ve updated the FAQ 
to reflect this new information. Here’s an excerpt:
“An error has occured; the feed is probably down.”
This widget relies on WordPress’s feed parsing abilities (look in
wordpress/includes/rss.php). WordPress grabs the requested feed then passes it to this widget for formatting. If you are seeing this error, it means one of three things:
- The feed really is down. Wait a while and try again.
- Your host is blocking WordPress from fetching the feed (very likely). Read more here
.
- WordPress’s feed parser isn’t working. Try updating to the most recent version of WordPress. If that doesn’t work, file a WordPress bug report in Trac.
In any case, you may want to first try using WordPress’s built-in RSS widget. If neither it nor my widget can display the feed, then you know for certain that it’s one of those three reasons causing the failure. (You’ll probably get the same error there, since the KB Advanced RSS widget uses the exact same error-checking method.)
Update: See also the suggestions in the comments below. (The first comment below is particularly useful.)