As you may or may not be aware Twitter updated their API and deprecated the old one. So now you can only access twitter feeds using oAuth authentication. If you are using latest version of Umbraco or .net4 with Umbraco you can make use of the excellent uTwit package created by none other than the legend that is Matt Brailsford.
If like me however you have some old Umbraco sites that you cannot for whatever reason upgrade to latest version of Umbraco or .net4 you can use my package TwitterOAuthOap. I am currently in the process of rolling it out to a few legacy sites and it works a treat!