I also have the game on steam as well, and when this update hit, it broke DirectX 11 rendering for ATI cards, which when you started a game and played for a bit (Random Interval some reports pegged at 5 minutes to as long as 30 to 40 minutes) The game would crash so bad it caused your display drivers to crash as well.

try to set -force-d3d9 on the command line, I dont know how to do this in galaxy yet, but I would just create a desktop shortcut and have galaxy running if you need to play MP.