Same thing happened with me. I have 16 GB of RAM and i7 processor. I had a 20 unit stack and a reinforcing 14 unit stack. Opponent had about 15 units. After a long battle of micromanaging to minimize unit losses it CTDs.
I had the unlimited men on bf turned on so ... gonna revert to false. Gonna try the LAA 4GB patch as well. As well as waiting 20-30 secs or a minute observing the unit kills and casualties ... before hitting the button that makes you go back to the campaign map.
EDIT: so far so good xD