How do you fix a disk authentication failure on Sims 3 in mac?

I have an iMac running snow leopard and a MacBook pro running lion. On both computers, I have the latest version of the game with no expansion packs. It works fine on my MacBook but always gives me the "disc authentication error" on my iMac. I don't know for sure if this will work for you, but you might try upgrading to Lion if you haven't already.