Assassin creed 2 keyboard

Hey Guys

Bought Assassin Creed 2 for Mac on Steam.
Everything worked great first time I played, however next time I opened it and every time since, my keyboard hasn't been working.
I have a Macbook Pro with a built in keyboard and trackpad mouse.
I am trying to play with a usb external keyboard and usb-wireless mouse.
Each time I open sometimes the Macbook Pro keyboard has worked but usually it doesn't at all either, and even when it does it is impractical to play the game on a laptop keyboard.

I have seen that many other Mac users have had this problem and it remains unresolved.

Thanks a lot