why would an rss address work in an rss reader but not in autoblog?

I've got autoblog working on my site for several feeds, but one of the addresses I'm using won't resolve. The address will work however if I paste it directly into a safari browser (which has a built in rss reader), then it resolves fine -- just not within autoblog. The address is feed://mentalhelp.net/images/root/rss/indices/weblog/www.mentalhelp.net.rss/ Any ideas on how to get this content posted by autoblog?

The error message I get is that feed can't be found. It also says "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." Unfortunately, I don't know what that means or how to do it.