I'm having the same problem over and over again. Just bought SMB via steam. I instal it and it runs absolutely fine. But the next time I try and run it it crashes without running at all - ie. just get the apple dialogue box saying SMB unexpectedly quit etc. etc.
I have tried deleting the info.plist file, but the only way i seem to be able to run the game again is by uninstalling via steam and then reinstalling. This takes a loooong time each time I want to play and I love the game!