So when you refer to the Dash showing up in widescreen, you are referring to the original MS Dash, right?
Your TV probably cannot autodetect 480p or 480i widescreen (however, it will autodetect 720p and 1080i in widescreen).
Take a look at the pictures, are they tall and narrow? If so, it just means you need to change the zoom mode, or aspect ratio of your TV to match. If you are saying the original MS Dash is going to widescreen though on your TV automatically, that seems to contradict my theory. AVAlaunch and dashes that support 720p and 1080i are another thing completely.