I call hax.
It was probably just some slow data (I think they're called 'packets', but I don't wanna use technical words in the wrong way :/) which caused it to resend, so the slow one got there about the same time the new one got there and caused it to show twice. I don't know that much about networking, but I have seen this kind of thing happen before. Kealper/Thoatt can explain it better.