In the HTC Weather widget, if you click on 'Weather' at the foot of the screen on one of the added/saved locations (not the 'current location'), you'll be taken to the AccuWeather site. Select Menu on that web page, top right, then My Settings, and when you press 'Use Current Location' you'll either resolve your problem or get an error message saying your Current Location can't be found.
I'm unsure as to whether the problem is at AccuWeather's end or HTC's, in that the information used for current location has either become unavailable to AccuWeather or that Accuweather aren't able to resolve the information themselves.
In the AccuWeather Help menu, there's a section on 'Issues with the Weather Clock' which suggests you contact the phone manufacturer not them, as they do not provide the widget, only the information.