Autoblog unable to understand Weebly RSS feed?

I am trying to import a RSS feed from Weebly. The URL is http://www.escofm.org/1/feed but Autoblog gives this error:

A feed could not be found at http://www.escofm.org/1/feed. A feed with an invalid mime type may fall victim to this error, or SimplePie was unable to auto-discover it.. Use force_feed() if you are certain this URL is a real feed.

(I’m not sure what SimplePie is.) The validate link on the dashboard reports the feed valid (although with a number of warnings). Other RSS readers (e.g., FeedGrabber, Newsblur, http://www.surfing-waves.com/feed.htm) can all parse the RSS feed. It seems like only Autoblog has problems with it.