[Plugin: FeedWordPress] Adding feeds doesn't work

Most times when I try to add a feed, I get no output.

If I add a page with multiple feeds, I get the message: This web page provides at least 2 different feeds. These feeds may provide the same information in different formats, or may track different items. (You can check the Feed Information and the Sample Item for each feed to get an idea of what the feed provides.) Please select the feed that you'd like to subscribe to. but then there is no text after that.

For a single RSS feed, it simply shows Feed Finder: Subscribe to slashdot.org then no more output.

Debugging is on, but provides no error messages or any other output.