As far as I've seen, a twbx should perform the same as a twb.
Have you tried using the little refresh icon in the icon bar at the top of the view? (looks like a circle with an arrow in it)
Thanks Jamie...yes I have tried it to no avail. So I was wondering if having it all contained in one workbook would affect the refreshes. The only time I can see the updated data on the dashboard is when I logout then backin to Tableau server.
Huh... Sounds like you've got some sort of bug on your hands... I've never run into the behavior you're seeing. I would email tableau support about this.