There is a small defect in the Twitter JS file here: http://widgets.twimg.com/j/2/widget.js
As explained in http://drupal.org/node/1140764, there is an easy fix, but it would be much better to have it fixed upstream. I didn’t find contact information in the .js file, so I figured this would be the best place…
Thanks for the report; I’ll relay it to the team.
This should now be resolved. Let us know if you’re still having issues.