Maybe you could give us more information. You're saying that Blockland crashes on Mac OS X Mountain Lions? And you show us just an error message. Maybe you should check your Mac OS X version first. If the error repeats, then you should contact Badspot.
According to, that your Blockland didn't even started, means that no console log is available, which means that you maybe have a wrong Mac OS X version. I don't know if the "Mountain Lion" is a special operating system, but I believe this could be the point of the problem. If I'm wrong, then please correct me.
Greetings,
Dignity.