[Bug/Crash] Game breaks when attacking enemy unit in tactical

I've had this a couple of times now and it seems completely random. When I go to attack an enemy unit in tactical my unit will line up and prepare to attack but then nothing happens. And because the attack hasn't finished yet I can't end turn or do anything. If I force my PC to go to the desktop, there's an error message and once I dismiss it the game crashes.

I'm running Windows 7 64-bit.

I've uploaded my debug.err file here.