Ubisoft released two new Chaos Theory maps last year, but the update was quickly removed as it failed to work. The maps are now back complete with a new Polar Base versus map, but so are the problems.
If you are an Xbox user then go ahead and download the three maps as so far there are no reported problems. If, however, you are playing Chaos Theory on an Xbox 360 then you might want to wait a while. It appears that that updating the game with the new maps causes the game to freeze or simply not load.
According to reports on the game's official forums the only way to get the game working with the update is to delete all previous Chaos Theory saves before applying the update. Hopefully Ubisoft will fix the problem as deleting game saves is not ideal.