External Data Provider / RSS doesn't seem to work?
 

I am trying to use the RSS feed from my vBulletin forum to post in a widget for my Wordpress blog. All I really need to put in the widget is the RSS URL:

http://www.netbookreviews.com/forum/external.php

But it gives me a 404 error saying it's not found.

Is there some sort of setting I'm missing / need to change?

I already went to:

Admin CP > External Data Provider > Enable RSS Syndication = Yes

What can be the problem? I know it's not wordpress in this situation as I've had other issues getting it to show up elsewhere as well.