Ok, I havn't completely tested this, but whenever I build a command tank, the game crashes. I believe that it's the command tank because I get to rank 3, get the command tank building, start building the command tank, then go observe my overloard style tanks, and after a few minutes, the game crashes. I was playing online on hamachi only with my friends, no computers. And for the last many games, the game would crash, only after I built the command tank.
it may be a multiplayer issue. have you built one in single player?
the same thing happened with me a little while ago, twice i think...
i think right when some units got into the frenzy aura, (overlord type tanks) it crashed...
it was in Single Player