it has happened two or three times, once in combat and once or twice in the campaign, the entire floor, buildings and all, will start to fall and will disappear from view. I'm on a mac running OS X 10.7.5
Seems like sometimes, for some reason, the ground isn't set to ignore gravity! I'll see if I can figure out why. Thanks for the bug report.
it hasn't happened for a while so in no way is it game breaking. I love 6.0 by the way, can't wait till you get around to optimization though cause my ancient computer can't handle the dynamic lighting :)
I've had this happen recently. The ground took three enemy buildings with it, so that was cool. Game crashed though (I had too big a ship...), and I couldn't tell whether the buildings were considered destroyed or not.