This happens regularly on the 360. It happens on all maps, whether alone or with others. The game also crashes randomly, usually near the end of a game, sometimes during wave 10, but the most likely time is during the last ten seconds of the escape. Points& challenge progress are awarded up to the moment of the crash, however you lose the bonus for having less than four players, obviously. If playing solo, 3000 points is a lot to lose & is very frustrating. The symptoms of the crash are a sudden freeze of the picture & loss of audio. Friends report that I "leave" the XBOX chat party & go "offline". The console becomes completely unresponsive & the only remedy is to shut off power to the console & then restart it. Your game is locking up the XBOX 360 completely, much as Skyrim does.