I have the same problem, with the game eating all two gigs of ram I've got (despite theoretically only needing one) and then crashing. Obviously there is a memory leak somewhere. What I have done is to set the game to autosave every turn, so if it does crash, I can pick up from pretty much where I left off. Also though, there is usually some indication that it is about to hit this threshold, as the computer starts to do a lot of harddrive data swapping and the game starts to really slow down. Typically I will notice this and shut down the game myself.
I have found however that it seems a lot of ram remains committed even though the game has been terminated. If I reboot from that point, the crash comes much sooner than it did the first time. What I have started to do not, is to not just shut down the program when I see it swapping a lot, but to also reboot my computer, so as to totally clear the ram.