Maybe somewhat related, but I have also had a problem when starting this game[multiplayerrobot.com] as a host, with other windows users. I'm able to start the game and play my first turn, submit file to GMR via web, but next player gets this error[tinypic.com].

Just for comparison, I am also a linux user with a game going (http://multiplayerrobot.com/Game#14068), and after two turns in, I haven't heard any complaints from the other players yet. If I have problems in the future, maybe we could compare notes to see if your issue is reproducible.