One for instance is http://www.multibriefs.com/briefs/bmwcca/bmwcca.xml
The feed show's up in the feed in the sidebar so I know it works, but not as posts.
That particular file is probably only updated once a week on their end.
I do have other registered feeds that are updated more often, but same problem.
I can preview the feed and see the latest article. Import now doesn't do anything.