How do you play over email?

[teacherjames]

I'm trying to play an email game, but we can't seem to get started. Here is what I've done so far:

1) sent my 2h file to the host
2) he has started a game and sent back my trn file and his own trn file
3) I placed both of our files into a folder
4) I tried to play an existing game
5) the computer crashes everytime I try to start

What are we doing wrong?
Does it matter if I'm on a mac and he's using a PC?

Any help would be greatly appreciated!!!