Recently I tried using HandyLight in an area where 3G had just been turned on last month....and sharing would simply not work. The next day I travel to an area I've know to have 3G for several years and its fine. I tried this in three or four other locations, all separated by hundred(s) of miles, and its fine and it works as expected. The only time I get an issue is when I try using the app in the location where 3G was just turned on. I've been using tethering apps since Day 1 on the iPhone (July 31st 2008) with the release of NetShare. I'm not new to the game, so I don't think this is user error. Given my settings are in a location profile, and nothing is changing other than location, then the only answer I can see is that AT&T is doing something. I know some like to blame ATT for their failure to correctly configure something. However, since it works in all locations except for one, that is the only conclusion I can come to.