WordPress MU

I'm trying to set up a "planet" blog on an intranet to aggregate feeds from various other blogs. Every time I try to use the RSS widget, or FeedWordPress, or wp-o-matic, WPMU tells me the feed is not valid or doesn't exist.

Yet, when I load the feed in a browser or use it in a desktop-based feed reader, it's just fine. Feeds from public web sites seem to work just fine as well. It's just the ones hosted on this intranet WPMU installation that won't syndicate.

What am I not understanding, or what is broken here?

Thanks.

Don't know - although I must say I haven't tested on an intranet.

Can you think of anything in WPMU RSS functionality that absolutely has to have the ability to do an operation where something on the public internet needs to send information back to WordPress MU? Magpie RSS, perhaps? SimplePie? Those are two technologies that the FeedWordpress and WP-o-Matic plugins use.

*bump* I've run into this problem again. I'm on WPMU 2.5.6. Any help anyone can give me would be greatly appreciated.