Hello,
there is a problem with importing feeds to posts manually when the server is behind a proxy. When clicking on the button "CLICK TO FETCH FEEDS NOW" then always the error "There was a problem with fetching feeds. This is likely due to a settings problem or invalid feeds." appears.
This is because the function "wp_rss_fetchFeed()" in import_posts.php will always be used. The function "wp_rss_fetchFeed()" uses the class SimplePie_File directly and therefore the proxy setting from wp-config.php will not be used.
Reference: http://core.trac.wordpress.org/ticket/22207
Yours,
Erich Lerch