I think that it is the Sprint's 3G network problem. I went to New York for this weekend, and, on our way we were passing Baltimore where LTE network had recently been launched. The download/upload speeds were amazingly fast. In New York, there is still 3G, but it seems to work much better then here. I didn't have any problems with sending messages, images and even short videos to my wife's iPhone and my friend's Android phone. Also I didn't have upload lock ups in Speedtest app.