Hi again. Just to clarify; you wrote that you downloaded Machinarium to a thumb drive. So then you plugged that into your MacBook Pro and now the game is installed on your laptop, yes? Well it's possible that you won't have to re-download the game. Game installers from October 2009 need to have two patches applied to play without glitches. Install
Patch 1 first and then follow with
Patch 2. You'll find installation instructions at those links. If you're still having problems after applying those patches it's then likely that your thumb drive download was corrupted. In that case you don't have to pay for the game again, just write to support-at-amanitadesign.com, explain your situation, and a new download link will be sent to you.
Do let us know if that clears up your problem.