The current version of the plugin - 3.3 - breaks the rss feed if the "red Herring" option is enabled.
I am working on a fix that will prevent this.
If you need the feed for things like networkedblogs then uncheck this option. Personally, I don't worry too much about RSS users because they do not get the advertising and are often other websites stealing content.
The Red Herring option is now accounting for about 75% of all spam detected, so I will keep it turned on. I am stopping about 800 spammers a day on my websites, so Red Herring is stopping about 600 of these.