Widget shows list of tweets from specified user which are marked by a specified keyword.
Make sure your user screen name is right. Check whether you have tweets containing your specified keyword in your timeline. Verify that the number of tweets fetched is set high enought to include some of those. You can check your settings by typing http://twitter.com/statuses/user_timeline.xml?screen_name=&count= in your browsers address bar and see whether there are matching tweets.