Twitter API is really busy lately.
That causes delays and performance problems when you try fetching tweets with Twitter API via JSON or other methods.
For that matter, my sidebar tweets widget uses jQuery preload to prevent my whole site to hang until the widget gets a response from Twitter API. But then again there are times that widget gets stuck with the preload phase.
The good news is Yahoo has a great tool that pulls the tweets of a user and swipes @usernames and @comments and returns a clean feed with a fast response.