Problems with Tweetblender

I've used TweetBlender for a while, but recently I've noticed problems with it on a couple of sites.

Basically, the widget is set up correctly, but I'm continually getting an error message onsite saying "No Tweets found for @twitterusername.

You can see an example of it in the right hand column of my blog.

Has anyone else seen this - I can't figure out why it's happening? I assumed some kind of security change has been in place at Twitter's end, but I can't see this anywhere in my Twitter account and I've been working my way through the TweetBlender settings without much luck either.

Anyone help at all?