The file that is in your feed (
http://dl.dropboxusercontent.com/u/94117/TheListeners_Ep1.mp3) is working. iTunes can take from 1-3 days or more to change your listing. If you resubscribe to your feed in itunes, you will get the correct file.
You didn't ask, but I'm going to tell you anyway, that Dropbox is NOT a good place to put your podcast media for a couple reasons.
1. It's not CDN (Media Server) so performance is going to be bad
2. It's against the terms of service for Dropbox and sooner or later, they are going to kick you off for serving media from their service.
If you want true media hosting, check out blubrry hosting at:
http://create.blubrry.com/resources/podcast-media-hosting/ and if you want a free month of service to try us out, use the promo code mike
-Mike