I’m using the Mystique theme for my blog. Found this page on how to fix the twitter issue. From the readings here, I then created a new tab in the Mystique control panel which would allow setting of your own twitter username (so that you can change it easier later on if need to).
Just thought of sharing my tweak: Fixing the Mystique theme Twitter issue. I documented my change there, and the changed theme files are also available for download at the end of the page.
Hope this helps ??