Alex King, I am having Twitter Tools vs. FeedWordPress problems also.
Is there any way to get them to play nice? Are they mutually exclusive?
Error messages point to various parts of rss-related WordPress files: "Fatal error: Call to a member function do_blog_post_tweet() on a non-object in [...]/wp-content/plugins/twitter-tools.php on line 740."
This is a shame because being able to aggregate content via FeedWordPress and in turn, send that out to Twitter (automagically) is a stellar concept.
Note: some posts here attribute the problems to (FeedWordPress' install of) MagpieRSS, however, even after replacing all WP RSS files with the originals, still no joy.
Help us Alex-Wan Kenobi, you're our only hope! :)