This game is basically unplayable on mac for me. Every other time i start a game, it crashes, so i have to restart or, I for some reason can't select my commander. I can't even reconnect to the game because it crashes all the time.
See thread in my signature for OS X system and crash reporting instructions. If you can get a crash report, see if the error message matches anything on bugtracker. If you're not sure what look for, upload the file here and we might be able to pick out the important details.
