Crashes

Hello everyone, today i've crashed twice on Winter Wonderland during the final wave with four people. The game just closes itself with no message. The crashes happened on to completely separate computers and happened the exactly same way. I use two completely different emulators so it isn't that either. Does anyone else encounter this? It really ruins the game for me. I would really like it to stop. Any suggestions would be greatly appreciated but to me its just seeming like the game itself which is pretty sad.