One of the things that fell out of BottomFeeder as we moved from the old network library (a hack job I created back in 2002-2003) to NetResources was error reporting at the application level. With the 4.1 release, that's back. If you pull down Help>>View Error Log, you'll see something like this:

What you see there is a list of errors that happened during the last few rounds of network updates. If you want to clear that, just hit the "Clear" button. If you want more details, hit the "Save to File" button - one of the results for the screen above look like this:

Time: December 1, 2005 10:53:25.358Description:NetResources Error: <<Net.HttpObjectNotFound (404 Feed not found error: FeedBurner cannot locate this feed URI. )>> on url: http://dwlt.net/tapestry/getfuzzy.rdf

Which tells me that when that feed was last queried, a 404 popped up. BottomFeeder treats a 404 as transient (there's a gone error - 410 - that Bf will use to mark a feed as dead). You might want to watch for repeated 404 errors though - it probably means that the site should have issued a 410.