Im having this problem quite often. The plugin works fine, but I see that it uses the twitter search to get the tweets, and, apparently, sometimes it does not work very well.
the user http://twitter.com/casasassociadas has a lot of tweets.
But if you search for it, you dont find any!
Therefore the widget wont retrieve any tweets, but I can get them if I get it directly in the code with:
Anyone has experienced that and have a workaround?