It turns out WeatherBug is well aware of the problem and it has to do with a bug related to interval times and updates. They seem to be on top of the issue, trying to resolve it with Microsoft. But until an update for the app comes out, they evidently recommend you set the update interval to 60 minutes.
Now, we had that as our update time on our HD7 earlier today and it still wasn't updating, so your milage may vary. Let us know if it worked for you or like us, you simply went to the Weather Channel.