One of the feeds I import using Autoblog stopped working.

All the other RSS feed addresses are working fine, this one just stopped working around 2-3 weeks ago… Autoblog tells me “there are no new entries” in the feed, but when using other rss feed readers the newer feed shows up. When I test the feed it says “I have already imported the first post in the feed [then gives the name of a post from 2 weeks ago] so I would have stopped processing.” Any ideas what may be going on?