Do you have any error logs? they should be found in the same directory as the JAR file. If you have a file called error_log_server*.log, also post the server log, found in the logs directory, and we'll see what we can do.
EDIT: Also, if you can, describe the steps up to the crash. For the freezing, did the game freeze once you confirmed the attack? For the game crash, had any turns gone by at all?