My game is blocked since the last update; when starting the last stand, i get a message to change my leader; i need to change my player name to resume, but it's impossible to change that name....
Impossible how? Impossible that even if you tried to click resume it won't change? Or impossible because you want that name and you don't want to change it anymore?
If it's because of the first impossible that I mentioned, then try visiting the forums of Con Games: https://getsatisfaction.com/deadzone?view=recent. The developers of 'The Last Stand' can help you there. Just post your question and your game ID there and they'll get to you.
If it's the second, then maybe someone else has registered that name already. Remember that Con Games are preparing to implement the Communications System and the reason that you need to change your leader's name is they "need it to be unique so that you will be able to send and receive private messages."